Notes 1
5.
Develop the Habit of Asking Questions and Seek Answers
Don’t
hesitate to ask questions, be it to your physics teachers or classmates or
through online resources. If you have doubts about the correct answers, don’t
hesitate to consult with your instructor or peers for feedback. Having someone
validate your answers is a great way to ensure you’ve arrived at the correct
solution. Don’t be afraid to make mistakes either. Sometimes, arriving at an
incorrect answer is more valuable than getting the correct answer right away.
6. Get
in the (study) zone
Like
many subjects, but perhaps particularly those you’re having difficulty with, a
mastery of physics requires uninterrupted daily studying. What this means
is different for everyone: some people work best in a busy coffee shop, while
others need absolute silence and isolation.
7.
Familiarize Yourself and Review Common Mistakes
Familiarizing
yourself with common errors made by students in physics is another proactive
approach to mastering the subject. Common mistakes include misreading
questions, neglecting units, incorrect vector handling, or simple mathematical
errors. It’s also important to reflect on your work, identify patterns of
errors, and strategize ways to prevent them.
8.
Drill yourself on the core concepts
After
you’ve done your reading (in preparation for your next lecture), make sure you retain the
concepts by drilling yourself on the main ideas, definitions, and formula
you’ve encountered. Having these fundamental concepts memorized (or at least
understood) before you go to your next lecture will really help you follow
what’s going on in class.
……….
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
