Safety
Public transport and relying on others puts you in the hands of other drivers. One of the benefits of owning a car is control over the driver seat. Sitting in the driver seat gives you more control over the outcomes of your drive.
You can’t always account for other drivers on the road with you. However, if you’re a smart driver, you can be safe regardless of others. Being a smart driver means that you know when to use turn signals, go to the speed limit, or stop.
It’s essential toget a good car insurance provider. Even if you’re a safe driver, insurance can benefit you in case of unwanted events. Owning a car and getting insurance is a lifelong investment that is sure to benefit you in the future.
…………
MEASUREMENT
Measurement is the process of assigning numbers to a given physical quantity.
1.1 Physical Quantity
In describing the behavior of objects around us we have to consider to matter, space and time. A moving body covers distance with time and for an object to move energy is required. For the motion to take place, force must be applied. When an object is in the course of motion changes its speed within a given time interval we said that it is undergoing acceleration. In all this we have physical quantities which are measurable and whose values can be used in the mathematical expressions to give numerical description about the object in a question. The physical quantities are divided into two categories which are fundamental / basic quantities and derived quantities.
(a)Fundamental quantities
These are independent physical quantities such as mass, length and time. These quantities have both dimensions and standard units which can be expressed dimensionally.The dimensions of mass, length and time are represented as M, L and T respectively. The term dimension is used to denote the nature of physical quantity.
(b)Derived quantities
The physical quantities which are obtained from fundamental quantities are called derived quantities. An example of derived quantities are such as area, volume, density, speed, and momentum. These quantities can be obtained by combining the fundamental quantities in one way or the other. The following are the few examples:
(i) Area =Length Length
[A]= L × L =L²
(ii) Volume =Length × Length × Length
[V] = L × L × L
(iii) Density = Mass/Volume
[ρ] = M/V
(iv)Speed = Distance/Time
[V] = L/T =LT-1
DIMENSION
Dimension is the way in which the physical quantities are related to fundamental physical quantities.
DIMENSIONAL ANALYSIS
Dimensional analysis is the way of showing how physical quantities are related to each other.
The alphabets used to represent particular unit may be called a symbol. There are various systems in use for the same unit , however the symbol M,L and T are dimensionally used for mass, length and time respectively.
The dimensions of a physical quantity refers to a fundamental units contained in it. Any quantity which can be measured in mass unit only, may said to have the dimension of mass.
The derived units are based on the fundamental quantities and in many cases it involves more than one fundamentals in such case the dimension of such quantity is expressed in general as K(M)X(L)Y(T)Z where K is the pure numeral of x, y and z which indicate how many times a particular unit is involved.
The power to which the fundamental units are raised can be obtained and are called the dimension of the derived unit.
For example the area of a square whose sides are in m each.
1mx1m=1m2
The dimension of the area of a square 1m2 is;
(L) x(L)=L2; then area has the dimension of length.
The dimension of velocity can be obtained from the definition of velocity which is;
Velocity is the rate of change in displacement. Its unit is meter per second.
The dimension of the velocity V=L/T=LT-1
USES OF DIMENSION
Dimensions of physical quantities can be used in the derivation of formula, checking of homogeneity of the formula etc
Derivation of Formula
Dimensions are sometimes used as a tool in establishing relationship between physical quantities.
For example through observation one would like to establish the connection between mass (m), its velocity (v) and the work done(w) on it.
The following are steps to follow:
Form a statement that: Work is proportional to mass and velocity
i.e. W = k …………………(i)
Where k is the proportionality constant
Dimensions
Work = Force × Distance
W = F × S
Where F = ma
[W] = [F] [S] = [m] [a] [s]
= MLT-2L
= ML²T-2
[V] = LT-1
Substitute the dimension in equation (i)
M¹L²T-2 = kMxLyT-z
Compare and equate the indices of corresponding dimensions
For M: x = 1
L: y = 2
T: -y = -2 or = 2
Substitute for x and y in equation (i)
W = km¹v² or W = kmv²
This is an empirical expression for the work done to move the body and the body acquiring kinetic energy.
Through the experiment or mathematical analysis it can be shown that k = ½
Checking of homogeneity of the formula
Another area which dimensions can be useful is to check consistence of the equation. An equation with several of terms each with number of variables is consistent if every term has dimensions. In the process of proving consistency or homogeneity, we are supposed to show that the left hand side of the equation is dimensionally equal to the right hand side of that equation. As an example let us consider the third Newton´s equation of motion
v² = u² + 2as
Where v, u, and s are final velocity, initial velocity, acceleration and distance respectively. Dimensionally
[v²] = [u²] + 2[a] [s]
We get,
[LT¯¹]² = [LT¯¹]² +2[LT¯²][L]
L²T ¯² = L²T¯² + 2L²T¯²
This shows that each term in the equation above represents dimensions of the square of velocity.
To convert a physical quantity from one system of units to another
The value of a physical quantity can be obtained in some other system, when its value in one system is given by using the method of dimensional analysis.
Measurement of a physical quantity is given by X = nu,
u – Size of unit,
n – Numerical value of physical quantity for the chosen unit.
Let u1 and u2 be units for measurement of a physical quantity in two systems and let n1 and n2 be the numerical values of physical quantity for two units.
n1u1 = n2u2
Let a, b and c be the dimensions of physical quantity in mass, length and time
M1, L1, T1 and M2, L2, T2 are units in two systems of mass, length and time.
This equation is used to find the value of a physical quantity in the second or the new system, when its value in the first or the given system is known.
Determination of units
At time when solving problem using an expression involves number of variables raised to some powers, the final unity of quantity being calculated may not be immediately recalled. One way of finding what unit is, is by making use of dimension. For example if unit of gravitation constant g after substituting the numerical values in the formula and evaluate the value, from the basic equation we have;
G = Fr²/Mm
Dimensionally,
[G] = [F][r²]/[M][m]
Where, [F] = MLT-2
[r²] = L²
[M] = M
[m] = M
Therefore, [G] = MLT-2L²/M²
= M-1L³T²
Since M¯¹ = Kg-1 , L³ = m³ and T-2 = s-2 , the units of G are m³s-2kg-1 which can also be written as Nm²kg-1
Limitations of dimensional analysis
There are shortcomings in the use of dimensions for the cases we have considered above. In the case of deriving empirical expressions, dimensional method cannot be used to derive trigonometric, logarithmic and exponential formula. As far as checking homogeneity is concerned, dimension method cannot detect the presence of dimensionless constant in the equation,can not be used to find dimensions of physical quantities with more than three fundamental quantities. It is restricted to only mass, length and time.
Example 1
After being deformed and then let free, a drop of liquid vibrate with a frequency which appears to depend on the surface tension of drop, the density ρ of the liquid and radius r of the drop. By means of dimensions, derive an expression for the frequency of vibration.
Solution
Frequency f depends on
(i) Surface tension
(ii) Density
(iii) Radius
These are connected together by the equation
f = k
Dimensions [f] = T¯¹, [] = MT¯², [] =ML¯³ and [r] = L
Substitute these dimensions in the equation above and simplify to get
M0L0T-1 = k
M0Lâ°T-1 = k
Equate the indices of corresponding dimensions
For M: x + y = 0…………….. (i)
L: -3y + z =0……………… (ii)
T: -2x = -1…………………. (ii)
Solving simultaneous equations we have,
x =1/2 , y = -1/2 and z = -1/2
f = k = k = k(γ/ρr)1/2
Exercise 1
- (a) Distinguish between a fundamental physical quantity and derived physical quantity?
(b)What is the dimension of physical quantity?
(c) Write the quantities below in dimension form
(i)The coefficient of viscosity
(ii)The surface tension
(iii)The gravitational constant
- (a) State the uses and limitations of dimensions
(b)Find out whether or not the equation below is dimensionally homogeneous
V/t = k(Prâ´/
Where k, v, t, p, r, η and L are dimensionless constant, volume, time, pressure, radius, viscosity constant and length respectively
(c) A wave is produced in taut wire by plucking it, the speed of the wave is said to be dependent on tension T of the wire, the mass M and length L. Using this information derive an empirical equation for the speed of the wave in wire.
- A ball bearing of radius r is released from the surface of the viscous liquid of viscosity constant η in a tall tube. The bearing attains maximum velocity v as it falls through the liquid. Given the friction force opposing the motion of the ball as;
F = k
Find numerical value of x, y, and z
- (a) A student in examination write s = ut + at² as one of the equations of motion he goes on to check dimensionally its homogeneity and he gets satisfied that he has quoted the write equation. What is the problem with the formula?
(b)The volume of the fluid flowing through a narrow tube per unit time depends on pressure gradient , viscosity constant η of the fluid and radius r of the tube. Obtain the expression for time rate of flow Q.
- (a) the periodic time T of a simple pendulum is assumed in the form of
T = k
Where k, m, l and g constant, mass of the bob, length of the thread, and acceleration due to gravity in the same order, Find the numerical values of x, y, and z. Give your comment on the expression.
(b)A force experienced by an object moving in a circle depends on mass m of the object, the velocity v at which it moves and radius r of the circle it describes. By using dimension obtain the expression for the force.
1.2 ERRORS
Error is the deviation of measured value from the exact value.
Physics is the subject which deals with measurements of physical quantities such as mass, length, time, temperature, and electricity to mention but a few. The instruments which are used in measuring that quantity are varying depending on nature and magnitude of the quantity being measured. For instance the instrument requires to measure the height of man may not necessarily to use the same instrument for measuring the waist or diameter of his hair strand. The scales on instruments are varying degrees of accuracy. This type of length measured by meter rule is not the same as that measured by micrometer screw gauge. The scale on meter rule is less accurate than the scale on micro meter screw gauge. When measuring time, the scale on stop clock is not accurate than that on digital stopwatch
Accuracy of number
There are different categories of numbers, Our interest will be on two types of numbers, the counting numbers and decimal numbers. These numbers are used more often. The numeral like 1, 2, 3 etc are used denote number of complete objects which naturally do not exist in parts or fractions. The numbers such as 1, 2, 2.5, 3.0 etc are known as decimal numbers because they consists some fractions. All scientific measuring instruments bear scales that cater for decimal number and for this matter all values read from measuring instrument must be recorded in decimal form and the answer after calculations using decimal numbers should be written in standard form A ×
Where A lies between 1−9 (1 and n can be positive or negative integers.
Below we have a 5 numbers written in various accuracies:
5 (accurate to nearest unit)
5.0 (accurate to nearest tenth)
5.00 (accurate to nearest hundredth)
5.000 (accurate to nearest thousandth)
Etc.
The more decimal places the more the accurate is the number.
ERROR ANALYSIS
Errors are involved in all measurements. There is a need to know the effects of errors in final results. When one has obtained a result, it is important to have some indication of its accuracy. For instance error of length measured by a meter rule may be given as x± 0.5 mm where x is the measured value and 0.5mm, is half of the smallest unit in measuring x which is considered as an error in measurement.
There are two main types of errors;
- Systematic errors
- Random errors
SYSTEMATIC ERRORS
These are errors due to experimental apparatus e.g an incorrect zero adjustment of the measuring devices (beam balance, voltmeter, galvanometer) Starting or stopping the clock, scale calibration, use of incorrect value of constant in calculation.These types of errors have a tendency of affecting reading in the same direction.
MINIMIZATION OF SYSTEMATIC ERROR
These cannot be corrected by arranging a large number of reading. They must be recognized in advance by means of careful survey. These errors can be determined by suitable treatment of observation or careful setting of apparatus over the zero reading check up before using the instruments.
RANDOM ERRORS
These errors gives a spread in answer of repetition equally, likely to be in either direction. These have equal chance to be –ve or +ve. They are caused due to;
- Fluctuation in the surrounding e.g temperature and pressure..
- Lack of the perfection of the observer due to parallax.
iii. Insensitivity of the instrument/apparatus.
MINIMIZATION OF RANDOM ERROR
- These errors can be minimized by repeating observation of a particular quantity.
- Experiments should be carefully designed, use of highly sensitive instruments and finding mean of the measured value,
- An experiment is accurate when the systematic error is relatively small.
MISTAKE
A mistake is done when the measurement is carried out in wrong way and as a result an error is introduced in value recorded. For example using instrument without checking for zero error or arrange instruments without following instructions properly can cause unnecessary errors which can otherwise be avoided.
PRECISION OF ERROR
This indicate the closeness with which measurements agree with one another quite independent to any systematic error.
BLUNDER
This is a mistake done several times.
How to avoid or minimizing errors
It is possible to avoid or if not to minimize by the first reading the instructions of a given experiment and undertaking them. Apparatus should be checked thoroughly before put them into uses. In most cases diagrams are given to show how apparatus must be arranged and connected, so follow the instructions. The apparatus must be securely connected to avoid accidents in the middle of the experiment. The following are some of precautions to be taken in minimizing the error in each case:
(i) Instrumental errors
In this case of errors that arise from measuring devices themselves, the precautions should be:
Regular maintenance and repair of apparatus
Proper storage of apparatus in special ductless rooms
Careful handling of apparatus when transferring them between places
Regular dusting, cleaning and oiling
(ii) Observation errors
The precautions to be taken to minimizing these kinds of errors during experiment are as follow:
Avoid parallax by reading the value from the scale perpendicular from position
Study the scale of instrument before operating it
Fix the apparatus according to the instructions and securely as possible to avoid unnecessary movement during experiment
Write the values read from the scale within the accuracy of instrument
Record the values actually made but not imaginary or cooked ones
(iii) Adjustment errors
It is good practice to check apparatus including measuring devices before put them into use. Together with checking the observer must:
Adjust the measuring device to remove zero error and where it is not possible record it somewhere for further reference
Fix each item of the apparatus in the right position and more importantly for instruments like meter rules, thermometers etc must kept vertical or upright
(iv) Random errors
In situation where every trial gives a different value, it is advisable to take as many as measurement as possible and find the average. A good example is determination of the diameter of wire. It good to take the measurement in different positions along the wire and the average value calculated. This is because the wire may not be uniform, so taking only value may not give the best results.
Accuracy of measuring instruments
(a) The meter Rule
The accuracy of the measuring instrument depends on the smallest unit it can possibly measure. We shall use the instruments for measuring lengths to explain this concept of accuracy. Take an example of a meter rule in fig 1.1 the total length it can measure is 1m which is subdivided into 1000 partitions each 1mm long. Thus the smallest length a meter rule can possibly measure is a millimeter. This means that the accuracy of a meter rule is 1 part out of 1000 parts that make the whole.
(b) The vernier calipers
The Vernier caliper is the measuring device for determine inner and outer diameter of hollow objects like test tubes, pipes etc. It has got two scale the main scale and vernier scale. The main scale reads up to one decimal place where as vernier scale reads up to the second decimal point of centimeter. Fig 2.2 represents the schematic diagram of vernier calipers.
How to operate it;
Before taking the measurements, the gap between fixed outer jaw and movable jaw and movable jaw is closed by pushing a roller. When the gap is closed, zero mark (first line) on the vernier scale must coincide with zero mark (first line) on the main scale not seen in the diagram. To measure inner diameter of the hollow objects, the inner jaws are pushed inside the object and the roller used to move the jaws apart until they touch the inner wall of the object. The screw is tightened to avoid accidental change in distance. The scales are read and values are recorded as;
= value on the main scale + Value on vernier scale
For the outer diameter, the outer jaws are opened and the object placed in between. After tightened the screw the scales are read once again and value recorded as;
=Value on main scale + Value on vernier scale
The smallest unit the vernier calipers can possibly measure is 0.01 cm or 0.1 mm. Thus the error that can arise as a result of using the device is therefore
OR
D =3.8 + 0.05
=3.85 cm
To read this value, the units cleared by zero mark of the vernier scale are first counted i.e. 3.8 and the value between 0.8 and 0.9 is obtain by looking for the line on the vernier scale that coincide with the line on the main scale and that is line number 5 on the vernier scale. Because this value is supposed to be the second decimal of a centimeter, it is recorded as 0.05 cm
(c) The micrometer screw gauge
Another very important measuring instrument is a micrometer screw gauge. It measures the length of the magnitude of 1 mm and less. There two scales on the device the sleeve scale and thimble scale as shown in fig 1.4
A micrometer screw gauge is used in measuring diameters of the wires thickness of the metal sheets, diameter of ball bearings and other tiny lengths. Before using it the gap between anvil and spindle has to be closed to check for zero error. An object to be measured is placed between anvil and spindle. By means of ratchet to make sure the object is gently held. Stop screwing when the ratchet makes the crackle sound. The value of the diameter obtained is the sum of the readings from the sleeve scale and thimble scale i.e.
Figure 1.5 shows the procedure for reading and recording the value from two scales. The carries a millimeter scale along horizontal line on the upper side of line each interval represents 0.5 mm. The scale on the thimble has 50 units all round such that when the thimble turn once, it either advances or retreats by 0.5 mm along the sleeve. This means that;
50 divisions = 0.5 mm
I.e 50 × 1 division = 0.5 mm
1 division = 0.5/50 = 0.01mm
Thus the smallest unit that a micrometer screw gauge can possibly measure is 0.01 mm
From the fig 1.5 the reading can be recorded as follow:
d = × 0.5 mm
= (6.00 + 0.09) mm
= 6.09 mm
This means that the diameter of wire
d = reading on sleeve scale + reading on thimble scale
The reading on the sleeve scale is found by counting the interval cleared by edge of the thimble and these are 6, meaning 6.00 mm. The value on the thimble is obtained by looking for the line on the thimble that coincide with the horizontal line on the sleeve which happen to be line number 9. These are 9 unit outs of 50 units round the thimble that make 0.5 mm
i.e. of 0.5 mm.
Absolute error
The absolute error is the magnitude of an error regardless of the sign. If d is the quantity then is an error positive or negative such that d = d0 where d0 is an actual value. The absolute error in d therefore is written as |
Relative error
The absolute error alone shows the size of error but does not tell how serious the error is in relation to the actual value. By taking the ratio of error to the actual value we can see how many times an error is as big as the actual value. This is known as relative error is expressed in decimal number.
Relative error =
If | = absolute error in x and x0 = actual value of x, then the relative error is given as:
=
Percentage error
The relative error expressed in decimal form multiplied by 100 gives percentage error. It is more convenient to express in percentage rather than as fraction or decimal number. The percentage error is written as
× 100
Calculation of errors
In experiment the measurement is done to more than one parameter and the values it obtained are substituted in a mathematical expression the gives the relationship between the parameter involved. The parameters concerned may require the same measuring device or different devices such as a meter rule and a micrometer screw gauge or a thermometer and a stopwatch. As we have seen above these instruments have differed accuracies and therefore contributing different errors in the values obtained. Using the values in a formula, the result is likely to contain a compounded error. Therefore, it is important to find the ways of calculating the error in the result. We are going to look; the operations such as addition, subtraction, multiplication and division of errors. Fin; we shall deal with compounded error in expressions involving indices.
(a) Addition of errors
Consider two quantities x and y given as x = x0 and y = y0 respectively.
Their sum s is s = x + y. We would like to find an error .The procedures are as follow:
The range of x is x–
The range of y is
The maximum possible sum is = (
The minimum possible sum is =
The absolute error in S is = [ +]
=
= [
=
From the results, the absolute error in the sum of two quantities is S the individual error in those quantities. Therefore the sum
S = S0
Where S0 = (x0 + y0) the sum of the actual values of x and y.
We can easily find the relative error and the percentage error in S as
and ⃒ × 100
(b) Subtraction of error
To subtract is to find the difference. Taking the same quantity x and y, let the difference between them be d = x-y; the error in d is found as follows:
The range of x and y are -+ and – respectively.
The maximum possible difference = ( +-
The minimum possible difference = (-+
The absolute error in d
= -]
= ++
=
In far as addition and subtraction of quantities are concerned, error are always added not subtraction.
(c) Multiplication of errors
For quantities x and y consisting of errors and respectively multiplied together, the product p contains an error found as follows:
The product of x and y is
The maximum possible product
= (++
=++
The minimum possible product
= (-
=-
The absolute error in p therefore is
= -]
=
=
The relative error in p,
⃒ = =+
(d) Division errors
If y is divided by x, a quotient q is formed, that is q =. The results is supposed to be represented as q = . The error in q is found by the following procedures:
The range of x and y are and
The maximum possible quotient,
The minimum possible quotient,
The absolute error in q is therefore,
=
=
Take (x-as LCM multiply we have;
= )
As
=
The relative error can be calculated as
⃒⃒ = +
Example 1: Two quantities x and y have values (10and (50.01) respectively. F int the absolute error, relative error and percentage error in their;
(a) Sum S
(b) Difference d
©Product p
(d) Quotient q = y/x
Solution
(a) Given x =
For the sum, ⃒= ⃒
and
=0.02
The relative error in s is ⃒⃒ where = (+), = 10 and = 5
⃒ = 0.02/15 =0.0013
The percentage error is
⃒⃒ ×100 = 0.0013 ×100
= 0.13%
(b)For the difference ⃒ =
= 0.01 + 0.01
= 0.02
Relative error in d is ⃒⃒ where = (
⃒0.02/5 =0.004
Percentage error is
⃒⃒ × 100 = 0.4%
(c) For the product p =
The absolute error ⃒ =
= 10(0.01) +5(0.01)
= 0.10 +0.05
= 0.15
The relative error in p is
⃒= 0.003
The percentage error in p
⃒ × 100 = 0.003 × 100
= 0.3%
(d) For the quotient, q = where /
The absolute error in q is ⃒= (
= 10(0.01) +5(0.01)/ =0.015/100 = 0.0015
The relative error in q is
⃒ = 0.0015/0.5 = 0.003
The percentage errors in q is therefore
⃒⃒ × 100 =0.003 × 100
=0.3%
Use of natural logarithms in error analysis
The calculations of errors we have seen above are used in simple cases with only two parameters to deal with. There are situations where the mathematical expressions into more than two variables raised to some powers in which case .using the method above. may not be adequate to produce the answer required. Application of logarithms may / quicken the process towards the answer. As an example, consider the following problem:
Example 1.2: A quantity Q is connected to another quantity p, r, and η by the expression
Q = ðœ«p/8lη . Obtain an expression for
(i) Relative error in Q
(ii) Absolute error in Q
Solution
Given that Q = ðœ«p/8lη
Take natural logarithms on both sided of the equation
/8lη)
Differentiating this we get
0///η
(i) The relative error in Q is
=
(ii) The relative absolute error in Q is
⃒⃒⃒
The absolute error in Q is
Q| = [||] + 4|| + || + ||] Q0
Exercise
- State the accuracy of each of numbers below
i/7 ii/3.2 iii/5.00 iv/11.03
- (a) give the difference between error and mistake.
(b)Mention the types of errors and their sources.
(c) Explain how you would minimizing the magnitude of random error in an experiment.
- (a) State the smallest unit each of instruments below can possibly measure and mention possible errors
(i) The meter rule
(ii) The vernier caliper
(iii) The micrometer screw gauge
(b) A box P contain smaller packages, and weighing (120.2) kg, (200.35) kg and (160.25) kg respectively.
(i) State the range off mass of each package
(ii) Calculate the absolute error in the mass P
(iii) What is relative error in mass P
(v) Determine the percentage error
- (a) Imagine you are doing an experiment on a simple pendulum to determine the value of acceleration due to gravity g at your location. What are possible errors are like to affect your result and what precaution will you take?
(b) Find the maximum possible error in the measurement of force on the object of mass M moving with velocity V ALONG THE CIRCULAR PATH OF RADIUS r given that M, V, and r are (3.50.1) kg, (201) ms-1, and (12.5 m respectively.
- During the experiment to determine acceleration due to gravity by using simple pendulum, the length l of the pendulum and periodic time T were measured an recorded as (1200.1) cm and (2.250.01) s respectively. Given the relationship between l, g and T is; T = 2 ,
Calculate;
(i) Absolute error in g
(ii) The percentage error in g
- (a) What is the meant by relative error?
(b) A quantity Q is expressed in terms of other quantities F, A, v and by the equation
Q =
Where F= 50.21, A= 0.050.005, and
Calculate the percentage error in Q
- (a) Distinguish between random error and systematic error
(b) Four trials in experiment of the diameter of the wire gave the diameter values 0.2 mm, 0.25 mm, 0.23 mm and 0.22 mm.
(i) What is the diameter of wire if each reading contains an error of 0.001?
(ii) Calculate the absolute relative error in the cross-section of the wire.
(c) Fig 2.6 shows parts of vernier calipers adjusted during the experiment
…………
Earth’s atmosphere is divided into five main layers, the exosphere, the thermosphere, the mesosphere, the stratosphere and the troposphere. The atmosphere thins out in each higher layer until the gases dissipate in space. There is no distinct boundary between the atmosphere and space, but an imaginary line about 110 kilometers from the surface, called the Karman line, is usually where scientists say atmosphere meets outer space.
TROPOSPHERE
The troposphere is the layer closest to Earth’s surface. It is 10 km thick and contains half of Earth’s atmosphere. Air is warmer near the ground and gets colder higher up. Nearly all of the water vapor and dust in the atmosphere are in this layer and that is why clouds are found here.
Lapse rate is the rate of fall of temperature in degrees per kilometer rise. It has an average value of 6 0C per km in the troposphere.
Tropopause is the upper boundary of the troposphere.
Importance (uses) of troposphere
- Controls the climate and ultimately determines the quality of life in the atmosphere.
- It supports life on earth. It contains oxygen which is used to respiration by animals.
STRATOSPHERE
The stratosphere is the second layer. It starts above the troposphere and ends about 50 km above ground.
The temperature of the stratosphere slowly increases with altitude. This temperature increase is due to the presence of Ozone layer which absorbs heat from the sun in the form of ultraviolet light.
The Ozone layer occupies the middle of stratosphere between 20 and 30 km it consists of Ozone formed by oxygen molecules dissociated and reforming into 03.
The air here is very dry, and it is about a thousand times thinner here than it is at sea level. Because of that, this is where jet aircraft and weather balloons fly.
Stratopause is the upper boundary of the stratosphere.
Importance (uses) of stratosphere
The stratosphere prevents harmful ultraviolet radiation from reaching the earth. Ozone absorbs harmful radiation from the sun. The Ozone protects plants and shield people from skin cancer and eye cataracts.
MESOSPHERE
The mesosphere starts at 50 km and extends to 80 km high. The top of the mesosphere, called the mesopause, is the coldest part of the Earth’s atmosphere with temperatures averaging about – 900C. The temperature of the mesosphere decreases with altitude (because there is no ozone to absorb heat).
This layer is hard to study. Jets and balloons don’t go high enough, and satellites and space shuttles orbit too high. Scientists do know that meteors burn up in this layer.
Importance of mesosphere
Mesosphere, thermosphere and exosphere prevent harmful radiation such as cosmic rays from reaching the earth surface.
THERMOSPHERE
The thermosphere extends from about 80 km to between 500 and 1,000 km. Temperatures increases as it approaches nearer to the sun. The heating effects of the earth no longer exist at these higher altitudes.
The thermosphere is considered part of Earth’s atmosphere (the upper atmosphere), but air density is so low that most of this layer is what is normally thought of as outer space. In fact, this is where the space shuttles flew and where the International Space Station orbits Earth.
This is also the layer where the auroras occur. Charged particles from space collide with atoms and molecules in the thermosphere, exciting them into higher states of energy. The atoms shed this excess energy by emitting photons of light, which we see as the colorful Aurora Borealis and Aurora Australis.
EXOSPHERE
The exosphere, the highest layer, is extremely thin and is where the atmosphere merges into outer space. It is composed of very widely dispersed particles of hydrogen and helium.
The upper part of the exosphere is called Magnetosphere. The motion of ions in this region is strongly constrained by the presence of the earth’s magnetic field. This is the region where satellites orbit the earth
Note:
(i)The troposphere, stratosphere, and mesosphere are collectively forms the homosphere. These layers have the same chemical composition; 78% nitrogen, 21% oxygen, 1% argon and other gasses which sum to about 0.05%. The thermosphere is excluded due to different in chemical composition.
(ii) The upper atmosphere above 90 km is called heterosphere. The atmosphere is no longer a mixture of gases but separates into layers heavier ones forming the bottom layer.
VARIATION OF TEMPERATURE WITH HEIGHT
The temperature above the Earth surface varies as shown in the graph below.
The residence time, is the mean lifetime of a gas molecule in the atmosphere
THE IONOSPHERE AND TRANSMISSION OF RADIO WAVES
The ionosphere is the region containing high concentrations of charged particles ions and electrons.
The ionosphere is created by atoms absorbing U.V radiation, gamma and X – rays.
The ionosphere extends from the lower thermosphere 55 km to 550 km above the earth’s surface.
Ionosphere layers:
Due to difference in composition of the air in the ionosphere, the ionosphere is divided into layers.
(i) The lower layer, called D layer; this layer exists only in the day time at an altitude of 55 to 90 km above the earth’s surface. Ionization in this region is relatively weak.
(ii) The next layer, E – layer: this layer is between 90 and 145 km above the earth’s surface. It has a maximum density at noon but is only weakly ionized at night.
(iii) The top layer, the F – layer: At night exists as a single layer in a region of about 145 to 400 km above the earth’s surface. During the day it splits into two layers, F1 and F2.
The Ionosphere and Communication
The ionosphere plays an important role in communication. Radio waves can be reflected off the ionosphere allowing radio communications over long distances. However this process is more successful during the night – time.
Why Transmission is better at Night?
During the day: the ionosphere extends into lower atmosphere (D layer). In this layer there is high concentration of particles and so recombination of electrons and ions due to collision is more likely to occur. The leads to the radio waves being absorbed rather than reflected. Hence distant communications are poor during the day.
During the night: The D layer disappears due to decrease in ionization of molecules but recombination of electrons and ions still occurs at a fast rate. The radio waves are then reflected by E and F layers in which recombination of electrons and ions is rare hence there is less absorption of the radio waves.
EXAMPLES: SET C
Example 01: Necta 1985 P1
(a) (i) Distinguish between P and S waves, state clearly the difference between their speeds in a medium.
(ii)Draw a schematic diagram showing how one station on the Earth’s surface can receive P or S waves from a distant source and state which waves can be refracted by the Earth’s outer core.
(b) (i) Give a summary of the origin and composition of the ionosphere.
(ii) What is the net electric charge in the ionosphere?
(iii) Show graphically how electron density changes with altitude in the ionosphere.
Answers
(a) (i) P – waves are longitudinal compression waves which can pass through solid, gas and liquid, whereas S – waves are transverse shearing waves which cannot pass thorough a fluid (gas or liquid)
The speed of P – waves in a medium is approximately twice that of the S – waves hence P – waves are faster than S – waves.
(ii) Refer the diagram for the seismic wave paths
(b) (i) Ionosphere is the upper part of the atmosphere. The ionosphere is formed due to the ionization of gaseous atoms as they absorb ultraviolet radiation from the sun, gamma and X-rays.
(ii) The net electric charge in the ionosphere is zero.
(iii) Variations of electron density in the ionosphere Electron density increases from D to F layer
Example 02: Necta 1988/1993 P1
(a) What are the factors that influence the velocities of P – and S – waves?
(b) Explain briefly the characteristics property of seismic waves which is used to locate discontinuities in the earth’s crust.
Answer
(a) The velocities of both P and S – waves are influenced by;
(i) Density of the rock material (Media),
(ii) Moduli of elasticity.
(b) Speed is the characteristic property of seismic waves that is used to locate discontinuities
Between the crust and mantle there is abrupt change of density, which shows an abrupt change in speed of both P – and S – waves, a Mohorovicic discontinuity exists here. Both P – and S
waves travels across this discontinuity.
Between the mantle and the core there is the Gutenberg discontinuity only P – waves travel this discontinuity.
Example 03: Necta 1989 P1
(a) State three sources of heat energy in the interior of the earth.
(b) (i) How does temperature vary with depth of the Earth?
(ii) What are the factors that influence the flow of heat from the interior of the Earth?
Answers
(a) Refer notes
(b) (i) The temperature increases with increasing depth
(ii) The rate of heat flow (conduction) is given by
The heat flow from the interior of the earth depends on:
Thermal conductivity of the rock,
Temperature gradient of the rock
Example 04: Necta 1989 P2
(a) What do you understand by the terms?
(i) Solar wind,
(ii) Magnetopause
(iii) Magnetosphere?
(b) What are the various factors that contribute to the Earth’s magnetic field?
(c) (i) With the aid of a suitable diagram, illustrate the components of the earth’s magnetic field at a given point P in the earth’s atmosphere.
(ii) An electron whose kinetic energy is 10 eV is circulating at right angles to the earth’s magnetic field whose uniform induction is 1.0 x 10 Wbm-2. Calculate the radius of the orbit and its frequency in that orbit.
Answers
(a) (i) Solar wind is a continuous stream of fast moving charged particles in the atmosphere which are produced from flare (eruptions) from the sun:
(ii) Magnetopause is the upper boundary of the magnetosphere.
(iii) Magnetosphere is the upper most part of the exosphere consisting mainly of charged ions. These particles move under the influence of the earth’s magnetic field.
(b) Short term variations: Disturbances in the magnetosphere due to solar emissions, these charged ions travel and in the ionosphere they form ring currents which give rise to a magnetic field.
Long term variations: The molten inner core of the earth is partly ionized. The movement of this ionized core causes a magnetic field which contributes to the earth’s magnetic field.
(c) (i) refer notes (ii) refer electromagnetism
Example 05: Necta 1990 P1
(a) Define the term “isoseismal line”.
(b) Write short notes on each of the following regions of the atmosphere.
(i) Troposphere, (ii) Stratosphere, (iii) Exosphere
Answer: Refer notes
Example 06: Necta 1990 P2
(a) Explain clearly how P and S – waves were used to ascertain that the outer core of the earth is in liquid form.
(b) Giving reasons, discuss the temperature variation in atmosphere (above the earth’s surface).
Answers
(a) P – waves are longitudinal elastic, waves capable of passing through solids and liquids and S – waves are traverse elastic waves capable of a travelling through solids only.
As both waves are projected towards the surface from interior core only the P – waves are recorded. This shows that the outer core is in liquid form.
(b) From the ground level, the atmospheric temperature decreases steadily as altitude increases steadily as altitude increases up to the troposphere. Thereafter the temperature increases with altitude up to the stratosphere. The ozone of the stratosphere absorbs the incoming sun radiation hence the temperature increases. In the mesosphere there is no ozone thus there is a decrease (cooling) with increasing altitude. The heating effect of the earth ceases in the thermosphere so, the closer to the sun, the higher graph refer notes.
Example 07: Necta 1991 P2
(a) List down four physical changes that took place at a location just before onset of an earthquake at that particular location.
(b) Give brief accounts of the processes that give rise to:
(i) The earth’s magnetic field,
(ii) Volcanic eruptions
Answers
(a) Density of rocks, stresses faults and waves
(b) (i) Explain generation of the earth’s field in the atmosphere and the outer core.
(ii) The seismic or earthquakes waves result from a fracture or sudden deformation of the earth’s crust. Vast stresses do occur locally in the rocks being concentrated where the rocks are sliding over one another. In regions where pressure is reduced, pockets of molten rock called magma are formed. Once the rock has melted the pressure may force it into cracks and fissures in the surrounding solid rock. This may emerge above the surface as a lava flow or volcano.
Example 08: Necta 1992 P1
(a) What do you understand by the term ionosphere?
(b) Explain how short wave long distance transmission and reception of radio waves is more effective at night than it is during the day time.
Answer
(b) In the day time, the base of the ionosphere (D-layer) is at lower heights where the high concentration of particles allows for ionization and recombination of ions by collision. Because of this, radio waves are absorbed rather than reflected, so distance communication is poor.
During the night time, the D – layer disappear, the base of the ionosphere is higher thus the recombination of ions is rare and so less absorption of waves occurs. Obliquely transmitted waves therefore can be reflected for distant reception.
Example 09: Necta 1993 P2
(a) What is the origin of the earth’s magnetic field?
(b) The diagram below shows the structure of the Earth. Name the parts indicated by the letter A to F.
Answer
(b) A represents Mohorovicic discontinuity
B represents Gutenberg discontinuity
C represents core
D represents Mantle
E represents Epicenter
F is not clear to interpret.
Example 10: Necta 1994 P1
(a) Define the terms: angle of inclination (dip) and angle of declination (variation) as used in specifying the earth’s magnetic field at any point.
(b)The earth’s total resultant flux density BR in a certain country is found to be 5.0 x 10-5 T and the horizontal component is BH is 2.0 x 10-5 T. Calculate ;
(i) The vertical component, Bv, and
(ii) The angle of inclination in that country
Solution
(b) (i) The vertical component is given by
(ii) Angle of inclination is given by
Example 11: Necta 1994 P1
(a) (i) Name the lowest layer of the atmosphere and the lowest layer of the ionosphere.
(ii) State the importance of each of these layers.
(b) What is the ozone layer?
Answers
(a)(i) The lowest layer of the atmosphere is troposphere and the lowest layer of the ionosphere is called the D – layer.
(ii) The t troposphere supports life
The D – layer is important for communication purposes as it reflects radio waves.
(b)The ozone layer is within the stratosphere. In the ozone layer molecular oxygen (O2) is dissociated into atomic oxygen (O) which is then reformed into ozone (O3)
The ozone so formed absorbs ultra violet radiation thus protecting plants and shielding people from skin cancer and eye cataracts.
Example 12: Necta 1994 P2
(a) Illustrate the component of the earth’s magnetic field at a given point P in the earth’s atmosphere by a suitable diagram.
(b) Using a tangent galvanometer, explain how you could determine the earth’s magnetic field.
Answers
Example 13: Necta 1995 P1
(a) (i) which region of the solid earth includes the e earth’s centre?
(ii) On which region of the solid earth do the continent rests directly?
(iii) Which region of the ionosphere has the highest electron density?
(b) Briefly explain how earthquake can be detected
Answers
(a) (i) inner core (ii) crust (iii) F – region
(b) Detection of earthquake is done by recording or measuring the seismic waves generated by the earthquakes. These waves are recorded by instrument called seismograph.
Example 14: Necta 1995 P2
(a) Draw a well labeled diagram which shows the interior structure of the earth. Indicate also which part of the interior are in solid form and which are in liquid form.
(b) Name and distinguish the type of waves that are produced by an earthquake.
(c) Briefly describe the three ways in which signal form ground based transmitter can reach the receiver.
Answers
(a) There are four types of seismic waves:
Body waves – divided into P and S – waves
Surface waves – divided into love and Rayleigh
(b) A telecommunication problem.
Ground wave, sky wave and space waves
Example 15: Necta 1998 P1
(a) State any three magnetic components of the earth’s magnetic field
(b) The horizontal and vertical components of the earth’s magnetic field at a certain location are; 2.73 x 10-5 and 2.1 x 10-5T respectively. Determine the earth’s magnetic field at
the location and its angle of inclination θ
Solution
(a) Components of the earth magnetic field are:
Vertical component (which point vertically downward)
Horizontal component which comprise lf:
Eastly component (towards geographic north pole)
Northly component (towards magnetic north pole)
(b)
Example 16: Necta 1998 P1 B
(a) What is the origin of the earth’s magnetic field?
(b) The following diagram shows the main layers forming the interior of the earth name the layers indicated by letters A to G.
Answers
(a) Refer notes
(b) A = Earth’s surface, B = Crust, C = Moho discontinuity, D = Gutenberg discontinuity, E = outer core, F = Mantle and G = inner core.
Example 17: Necta 1998 B
(a) Explain the following terms; Earthquake, Earthquake focus, Epicenter and body waves.
(b) List down three (3) sources of earthquakes,
(c) (i) Define ionosphere
(ii) Mention the ionosphere layers that exist during the day time
(iii) Give the reason for better reception of radio waves for high frequency signal of night than during day time.
(d) Explain briefly three different types of radio waves traveling from a transmitting station to a receiving antenna.
Answers
(a) Refer notes
(b) Refer notes
(c) (i) During the day time all the layers D,E,F1, and F2 – layers exists.
(ii) Refer Necta 1992 (b)
(d) Ground (surface wave)
Space wave
Sky waves) (refer telecommunication notes)
Example 18: nectar 2000 P1
(a) With reference to an earthquake on a certain point of the earth explain the terms ‘focus’ and ‘Epicenter’
(b) What is importance of the following layer of the atmosphere?
(i) The lowest layer
(ii) The ionosphere
(c) (i) Describe two ways by which seismic waves may be produced.
(ii) Describe briefly the meaning and application of “seismic prospecting”.
Answers
(a) Refer notes
(b) (i) Importance of troposphere is supports life on earth
(ii) Ionosphere enhances communication over long distances.
(c) (i) Describe any two causes of earth quake
(ii) Seismic prospecting is an artificial production of seismic waves purposely for searching underground fuels and oils or gases
Example 19: Necta 2001 P1
(a) (i) Define the terms “angle of declination” as used in the specification of the earth’s magnetic field at a point
(ii) The horizontal component of the earth’s magnetic field at a location was found to be 26.0 while the angle of inclination was Find the magnitude of the field and the vertical component of the field at the location
(b) (i) Define an earthquake
(ii) Distinguish between P and S waves. What factors influence their velocities?
Answers
(a) (i) Refer notes
(ii)
(b) The velocities of P and S waves are influenced by;
Density, of the media
Shear modulus, of the media, and
Bulk modulus, B of the media.
Example 20: Necta 2002 P1
(a) (i) What is the importance of ionosphere to mankind?
(ii) Explain why transmission of radio waves is better at night than at day time.
(b) (i) What is an earthquake?
(ii) Explain briefly any four (4) causes of earthquake
Example 21: Necta 2003 P2
(a) Explain the following:
(i) Earthquake (ii) Earthquake focus (iii) The epicenter.
(b) List down three sources of earthquake
(c) (i) Define the ionosphere
(ii) State the ionosphere layer that exists during day time.
(iii) Give the reason for better waves reception for light frequencies signal at night than during the day time
Example 22: Necta 2004 P1
(a) (i) Explain the terms epicenter and focus as applied to earthquake.
(ii) State any four (4) indications that may predict the occurrence of an earthquake.
(iii) State and explain two variations of the earth magnetic field.
(iv) State one necessary precaution to be taken to people living in a region with a high risk of occurrence of earthquakes.
(b) Explain the following
(i) Solar wind (ii) Magnetopause (iii) Ionosphere.
Example 23: Necta 2005 P1
(a) Define the following terms
(i) Epicentral distance (ii) Body wave (iii) Seismograph
(b) (i) explain the meaning of reflection seismology state its application
(ii) Show how the magnetic field within the atmosphere is generated?
(c) (i) Name the lowest layers of the atmosphere and the ionosphere
(ii) State their importance
Answers
(a) (i) Lowest layer of atmosphere is troposphere and that of the ionosphere is the D – layer.
Example 24: Necta 2006 P1
(a) (i) State two (2) ways by which seismic wave may be produced
(ii) What is seismic prospecting?
(b) (i) Discuss briefly the importance of the lowest layer of the atmosphere and the ionosphere.
(ii) Sketch the temperature against altitude curve for the atmosphere indicating the important atmospheric layers.
(iii)The average velocity of P – waves through the earth’s solid core is 8kms-1. If the average density of the earth’s rock is 5.5 x 103kgm-3 find the average bulk modulus of the earth’s rock.
Answer
(a) (i) Causes of an earthquake
(b) (ii) using the formula
Example 25: Necta 2007 P1
(a) (i) What are the differences between P and S waves?
(ii) Explain how the two terms of waves (P and S) can be used in studying the internal structure of the earth.
(b) Write short notes on the following terms in relation to the changes in the earth’s magnetic field; long term (secular) changes, short – period (regular) changes, and short – term (irregular) changes.
(c) (i) What is geomagnetic micro pulsation?
(ii) Give a summary of location, constitution and practical uses of the stratosphere, ionosphere and mesosphere.
Answers
(c) (i) Geomagnetic micro pulsation are small rapid changes in the earth’s magnetic field. They have periods between 0.2 second and 10 minutes and intensities less than 0.01% of the minimum field.
Example 26: Necta 2008 P1
(a) Define the following terms:
(i) Earthquake (ii) atmosphere
(b) Distinguish between body waves and surface waves that are produced by an earthquake.
(c) (i) Define the terms epicenter and focus as applied to earthquake.
(ii) Draw a well labeled diagram which shows the interior structure of the earth.
Example 27: Necta 2009 P1
(a) (i) What is meant by the shadow zone?
(ii) Why does the shadow zone occur?
(b) (i) Name the lowest layer of the atmosphere and the lowest layer of the ionosphere.
(ii) State the importance of each of these layers in b (i) above
(iii) Explain briefly the reason for better reception of radio waves for high frequency signals at night times than during day times.
(c) State the sources of heat energy in the interior of the earth.
Example 28: Necta 2010 P1
(a) (i) Explain the terms: earthquake, earthquake focus and epicenter.
(ii) Describe clearly how P and S waves are used to ascertain that the outer core of the Earth is in liquid form.
(b) (i) Define the ionosphere and give one basic use of it.
(ii) Why is the ionosphere obstacle to radio astronomy?
Example 29: Necta 2011 P1
(a) (i) Define the following terms: Geophysics, Atmosphere and Epicenter
(ii) Write down brief notes on the location, composition and importance of the following:
Troposphere, Stratosphere, Mesosphere and Thermosphere
(b) (i) Draw sketch diagram showing the working part of a Seismometer.
(ii) Explain how temperature varies with both altitude and depth of the Earth.
(iii) Write down two factors that governs heat flow from the interior of the Earth.
Example 30: Necta 2012 P1
(a) (i) Name three layers of the atmosphere
(ii) Describe any two major zones of the earth.
(b) (i) What are the factors that influence the velocities of P and S waves?
(ii) The P and S waves from an earthquake with a focus near the earth’s surface travel through the earth at nearly a constant speed of 8 km/s and 6 km/s respectively. If there is no reflection and refraction of waves how long is the delay between the arrivals of successive waves at a seismic monitoring station at 900 in the latitude from the epicenter of the earthquake?
Solution
(a) (ii) any two of core, mantle, crust, hydrosphere, atmosphere
(b) (i) the density of rock, moduli of elasticity of rock material.
(ii) Illustration (R = earth radius)
| |
Distance travelled by the waves (distance between focus and seismic station) is
Time taken by P – waves to arrive at the station is
Time taken by the waves to arrive at the station is
The time interval between the arrival of the two waves is t = t2 – t1 = 25.1 = 18.9 = 6.2 minutes.
Example 31: Necta 2012 P1
(a) (i) What do you understand by the word environmental physics?
(ii) Briefly explain three effects of seismic waves.
(b) (i) Mention three types of environmental pollution
(ii) Explain on the following climatic factors which influence plant growth: Temperature, Relative humidity and wind.
Example 32: Necta 2013 P1
(a) (i) The main interior of the earth core is believed to be in molten form. What seismic evidence supports this belief?
(ii) Explain why the small ozone layer on the top of the stratosphere is crucial for human survival
(b) Electrical properties of the atmosphere are significantly exhibited in the ionosphere.
(i) What is the layer composed of and what you think is the origin of such constituents
(ii) Mentioned two uses of the ionosphere
(c) Briefly explain why long distance radio broadcasts make use of short wave
Answers
(a) (i) When P and S seismic waves are sent from one side of earth to the other, only P waves can be detected on the other side. The fact that S waves do not travel through the core provides evidence for the existence of a liquid core.
(ii) Ozone absorbs harmful radiation from the sun. The Ozone projects plant and shield people from skin cancer and eye cataracts.
(b) (i) The layer is composed of free electrons and positive ions. The ionosphere is created by atoms absorbing UV radiation, gamma and x-rays.
(ii) Uses of the ionosphere
Ionosphere supports radio communication over long distances
Particles in the ionosphere absorbs U.V radiation gamma and X-rays, thus protecting people from harmful effects of these radiations
(c) Refer telecommunication notes.
Example 33: Necta 2013 P1
(a) Briefly explain on the following types of environmental pollution:
(i) Thermal pollution
(ii) Water pollution
(b) Describe the soil temperature with regard to agriculture, physics which causes lower crop growth at a particular area
Answers
(b) High soil temperature causes the crop roots to rot, this leads to insufficient water supply to plant leaves and hence lower the growth of crop.
Lower soil temperature inactivates soil organisms. Decomposition of organic matter is lowered and hence the supply of nutrients to crop which in turn lead to lower crop growth.
TRY YOURSELF
(a) (i) What are auroras?
(ii) Define the homosphere
(b) (i) What are the factors which contribute toward volcanic eruptions?
(ii) What are the effects of volcanic eruptions?
(iii) What are lahars?
Lahars are rapidly flowing mixtures of rock debris and water that originate on the slopes of a volcano. They are also referred to as volcanic mudflows or debris flow. Volcanic eruptions may directly trigger one of more lahars by quickly melting snow and on a volcano or eject water from a crater lake. The form in a variety of at always including through intense rainfall on loose volcano rock deposits and as a consequence of debris of debris avalanches
ENVIRONMENTAL POLLUTION
Pollution is the addition of unwanted materials or pollutants into the environment.
Pollutant is any substance that does not belong in the natural system and disrupts the natural balance.
Type of Environmental pollution
(a) Air pollution (atmospheric pollution)
(b) Water pollution (hydrosphere pollution)
(c) Land (soil) pollution
(d) Noise pollution
(e) Thermal pollution
ATMOSPHERIC (AIR) POLLUTION
AIR POLLUTION
This is a form of environmental pollution caused by the release of gaseous materials and dust particles in the atmosphere. The main pollutants found in the air we breathe include, particulate matter, lead, ground-level ozone, heavy metals, sulphur dioxide, benzene, carbon monoxide and nitrogen dioxide
Causes of Air Pollution
Man made causes:
(i) Clearing (deforestation) and burning of vegetation. This releases carbon dioxide in the atmosphere and dust particles which may be carried by wind on bare land.
(ii) Burning of fuels: This releases green house gases in the atmosphere. Fuels are burnt in cars, power stations and industries.
(iii) Construction activities, like road, building, etc construction, can add dust particles in the atmosphere.
(iv) Automobile exhausts. Car, trains, etc burns fuels as they move his releases pollutant gases in the atmosphere.
(v) Smokes from industries also pollute the atmosphere.
(vi) Agriculture activities. The use of pesticide/insecticides pollutes the air.
(vii) Mining activities
Natural causes:
(a) Volcanic eruptions – release smoke and dust particles in the atmosphere
(b) Wind storms – carry land particles into the air
(c) Temperature inversion – the increase in temperature in the stratosphere causes high altitude particles to sink to the troposphere
WATER POLLUTION
Water Pollution is the degradation of water quality in a manner that disrupts/prevents its intended or original use.
Surface Water or Ground water may be polluted
Causes of water pollution
(i) Disposal of untreated sewage (industrial or hospital, etc) into the water bodies.
(ii) Wind may introduce dust particles into water from the land.
(iii) Agriculture activities near water bodies. Chemical used during farming may be taken to the water bodies by the rain water.
(iv) Oil spilt. The leakage of oil in under water oil pipe, leakage from boats, ships, etc pollutes the water.
(v) Fishing by using chemicals (dynamite fishing).
(vi) Volcanic activities along water bodies.
(vii) Quarrying along the coast.
LAND (SOIL) POLLUTION
Soil pollution is defined as the build – up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease causing agents which have adverse effects on plant growth and animal health.
A soil pollutant is any factor which deteriorates the quality, texture and mineral content of the soil or which disturbs the biological balance of the organisms in the soil.
Causes of soil pollution
(a) Chemical from industries
(b) Acid rain – this increase soil acidity
(c) Farming activities which make use of insecticides/pesticides
(d) Mining activities – increase rock sediment into the soil.
NOISE POLLUTION
Noise pollution is any disorganized loud sound.
Causes of noise pollution
(a) Noise from factories and workshops
(b) Thunderstorm explosion of bombs
(c) Low level flying aircraft
(d) Radio on large volumes
(e) Slamming of doors
