Light II

TEACHERS’ GUIDE

SUBJECT : PHYSICS

TOPIC : LIGHT

SUB-TOPIC : Lenses and Optical Instruments

CLASS : Senior Three

CLASS SIZE : 50 Learners

TIME REQUIRED : Minimum: 120 – 240 minutes

INTRODUCTION

Man has always had interest in observing things in a more detailed manner. Lenses or magnifying glasses, as they are sometimes called, have been used to observe objects. For example in study under microscope lenses are used to magnify tiny organisms that may not be easily seen by the naked eye, and in telescope lenses are used to magnify distant objects like the stars and moon. People with poor eye sight use lenses to enable them see better, for example use of reading glasses to enlarge prints, watch repairers and handset cell phone repairers also use magnifying glasses.

CONTENT

In this unit, the content covered will include:

• Types of lenses and their optical properties.
• Passage of standard rays through a lens.
• Power of a lens.
• Construction of ray diagrams.
• Properties of images formed by lenses.
• Magnification
• Experiments to determine the focal lengths of thin convex lenses.
• Human eye and eye defects
• Projector
• Simple camera

LEARNING OBJECTIVES

By the end of this unit the learner should be able to

1. Identify the different types of lenses.
2. Define the optical properties of lenses.
3. Define the power of lenses.
4. Construct graphically images formed by lenses using standard rays.
5. Describe images formed by lenses.
6. Determine magnification of images formed by lenses.
7. Determine the focal length of thin converging lenses.
8. Draw the projector and describe how it works.
9. Draw the human eye and explain how it forms images.
10. Draw the lens camera and explain how it forms images.
11. Explain the use of lenses in correction of eye defects.

Job related life skills

By the end of this topic, learners are expected to have acquired the following Job related Skills:

1. Personal attributes – self confidence, time management, creativity/imaginative, recording skills, enthusiasm, imagination and self awareness.

2. Communication – observation & listening skills, reporting in writing.

3. Team work – task oriented leadership skills, group work.

4. Problem solving - information seeking, environmental protection & conservation, seeking for information (research).

5. Applicability of number - numeracy (as they compare crop yields in treated and untreated plots) Problem solving - information seeking, environmental conservation, Reflective thinking.

6. Information Skills – ability to work with and present numerical data using appropriate intermediate calculations, ability to identify information needs, observe and collect evidence, present findings appropriately using graphs, charts, pictures and reports.

LEARNERS’ ACTIVITIES

Activities 1 to 4

In these activities, the learners investigate the optical properties of lenses.

Material required for each group

Bi-convex lens, Plano-convex lens, converging meniscus, bi-concave lens, Plano-concave lens, and diverging meniscus

Activity 1

• Learners examine the physical features of the lenses provided
• Learners use the lenses to view different objects and fill in the table below

	Type of lenses
	Bi-convex	Plano-convex	Converging meniscus	Bi-concave	Plano-concave	Diverging meniscus
Effect on size of object

Activity 2

Lenses in Art

• Learners magnify and draw in fine detail of at least one of the following: leaf, insect, bark of a tree, human skin.
• Display their work in class
• Discuss the use of magnifying glasses in Art

In the plenary, learners discuss the economic importance of using magnifying glasses in Art.

Activity 3

Lenses in hygiene

• Learners use magnifying glasses to view some living organisms in dirty water and record what they see.

In plenary, learners discuss the biological and economic importance of boiling water for drinking using their observations as a basis.

Activity 4

Lenses in sight seeing

• Using two convex lenses and a manila paper, learners construct a telescope and use it to view different sites in the neighbourhoods.
• Learners try out other groups’ telescopes and compare them with theirs.

In the plenary, learners discuss the different uses of viewing instruments in tourism, war and road construction.

Activity 5

Discussion

Topic: Discuss how you would use your camera to earn a million shilling in one year. The discussion should include: planning, budgeting, execution of the plan, saving procedures etc.

Note to the teacher: You may invite a resource person to help the learners to hold a fruitful discussion. He/she should be guided on the kind of things he/she should talk /not talk about.

ACTIVITY 6

In this activity learners will carry out experiment to measure the focal length of converging lens

Material required

Plane mirror, convex lens (f=10 cm or 15cm or 20cm), screen with a hole and wire gauge placed on the hole, torch bulb, two dry cells, bulb holder, connecting wires, lens holder, metre rule.

Instructions

1. Learners divide into groups and each group elects a chairperson and a secretary.
2. In this experiment you will determine the focal length of the given convex lens using an illuminated object and a plane mirror.

3. Set up the apparatus as shown in diagram above.
4. Adjust the position of the lens until a sharp image of the object (wire gauge) is formed on the screen alongside the object.
5. Measure the distance between the lens and the image. This distance is equal to the focal length of the lens.

In preliminary discussion

1. Each group presents their results.
2. Learners brainstorm on the applications of lens in projector, camera, human eye and use of lenses to correct defects in the human eye.

Teacher’s Notes

1. A simple lens is usually a piece of glass bounded by spherical surfaces.

2. Principal axis of a lens is the line joining the centres of curvature of its surfaces.

3. The principal focus of a converging lens is that point on the principal axis to which all incident rays on the lens, originally parallel and close to the principal axis, converge after passing through the lens. The principal focus of a converging lens is real.

4. The principal focus of a diverging lens is that point on the principal axis to which all incident rays on the lens, originally parallel and close to the principal axis, appear to diverge from after passing through the lens. The principal focus of a diverging lens is virtual.

5. The optical centre of a lens is the centre of the lens. All rays passing through the optical centre of a thin lens are drawn straight not deviated.

Standard Rays

For Convex lens

Position of object	Draw the ray diagram to show the location of images	Nature of image	M=h’/h
Between the Principal focus and the optical centre of the lens
at the Principal focus
Between the Principal focus and distance twice the focal length from the optical centre
at a distance twice the focal length from the optical centre
at a distance greater than twice focal length from the optical centre
at infinity

For concave lens

Position of object	Draw, using ray diagram, the location of the image	Nature of image	M=h’/h
between the focal point and the optical centre of the lens
at the focal point
between the focal point and distance twice the focal length from the optical centre
at a distance twice the focal length from the optical centre
at a distance greater than twice focal length from the optical centre
at infinity

For convex lenses:

1. There are three important rays in the ray diagram construction to locate the position of the image in thin lenses.

1. Ray from the object parallel to the principal axis
2. Ray from the object passing through the optical centre
3. Ray from the object passing through the principal focus

2. When the object is placed between focal point and optical centre, the image formed is behind the object, virtual, erect and magnified.

3. When the object is placed between the focal point and distance twice the focal length from the optical centre, the image formed is beyond 2F, real, inverted and magnified.

4. When the object is placed at the focal point, the image formed is at infinity.

5. When the object is placed at a distance twice the focal length from the optical centre, the image formed at the point twice the focal length is real, inverted, and the same size as the object.

6. When the object is placed at a distance greater than twice the focal length from the optical centre, the image formed is between 2F and F, real, inverted and diminished.

7. When the object is placed at infinity, the image formed is at the focal point.

8. The size of the image varies according to the position of the object from the optical centre

9. The linear magnification of the image is the ratio of the height of the image to the height of the object. I.e. m = height of image /height of object.

10. Power of a lens is the reciprocal of its focal length in metres. Power = 1/focal length in metres

Projector

Light source – Carbon electric arc or quartz iodine lamp to produce high intensity source of light and is placed at the centre of a concave mirror.

Concave mirror – Reflects back light otherwise wasted at the back of the projector

Plano-convex lenses (Condenser)-Collects and concentrates (condenses) light that would otherwise spread out and get wasted and converge it through the slide onto the projector lens.

Projection lens – Focuses the magnified slide image on the screen. This is done by moving the lens to and fro.

Link pages

http://en.wikipedia.org/wiki/lens_(optics)

http://www.physicsclassroom.com/Class/refrn/

Exercise

1. Describe the nature of the image when the object is placed

1. Between the lens and the principal focus
2. At the principal focus

2. List two uses of lenses
3. Define linear magnification.
4. What is a virtual image?

Answers

1. (a) magnified, upright, virtual

(b) at infinity

2. As magnifying glasses, eye glasses, etc.

3. Magnification = height of image / height of object

4. A virtual image is one which cannot be formed on a screen. It is formed where virtual rays meet.

SAMPLE SCHEME OF WORK

SUBJECT: PHYSICS

NAME OF TEACHER……………………………………....SCHOOL……..............……………….. TERM…......… CLASS…........… NO. OF PERIODS PER WEEK……………… YEAR……...….. NO. OF STUDENTS…………………

WEEK	PERIOD	TOPIC	SUB - TOPIC	OBJECTIVES	METHODS	TEACHING AIDS	REFERENCES	Comments
1	3	Light	Lenses and optical instruments	By the end of this topic, learners should be able to; -Define optical properties of lenses -Graphically construct images -Describe images formed -Calculate magnification	-Illustrates the types of lenses -Demonstrates the passage of standard rays through a lens -Illustrates the power of a lens -Discusses the properties of images	-Metre rule -Ray slit lenses	-
2	3	Light	Lenses and optical instruments	-Carry out experiments to determine focal length of a convex lens	-Experiments to determine focal length of a convex lens	Bulbs, bulb holders, cells and cell holders, connecting wires, Screen Cardboard with mesh wire Lenses.
3	3	Light	Lenses and optical instruments	-State and describe use of lenses -Draw a projector and describe how it works -Draw the eye and camera and describe how these form images	- Discusses the uses of lenses -projector -human eye and camera	Charts (camera if possible)

Lesson Evaluation:

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PHYSICS

SAMPLE LESSON PLAN

DATE	CLASS	SUBJECT	NO.OF LEARNERS	DURATION	TIME
…./…./…	SENIOR THREE	PHYSICS	50	80 MINS	8.00 – 9.20am

TOPIC : LIGHT

SUB – TOPIC : Lenses

Objectives : By the end of the lesson, learners should be able to:

1. Identify types of lenses
2. Define optical properties of lenses
3. Graphically construct images
4. State the nature of images formed.

Methods : Guided discovery

Demonstrations / Experiments

Question and Answer

Explanations

Teaching/Learning aids: Ray slits

Bulb and Bulb holders

Cell and Cell holders

Connecting wire lenses and Rulers

Chalkboard

Markers

Pictures/Photos

References:

Time	Theme	Teacher’s Activities	Learners’ activities
5 minutes	Types of lenses	-Distributes different types of lenses to groups -Instructs learners to study the properties of lenses (Activity 1)	-Learners examine lenses -explore properties of lenses
25 minutes	Standard rays	-using ray slits demonstrates passage of light through lenses -illustrates optical properties	- Observe -Draw the passage of standard rays through lens -Define the optical properties of lenses
40 minutes	Images formed by lenses	-illustrates drawing of rays to obtain images -instructs learners to draw images of objects at different distances from the optical centre Note: Diagrams should be drawn to scale.	-Draw the ray diagrams -Describe images formed
10 minutes	Images formed by lenses	-Guides learners to explore the properties of images formed by lenses practically.	-verify the properties of images formed by lenses practically.

Lesson Evaluation

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Machines

ELATE PHYSICS

UNIT 3

TOPIC : Machines

SUBTOPIC : Efficiency of machines

CLASS : Senior Three

NUMBER OF LEARNERS: 50

DURATION: 120 minutes minimum – 240minutes maximum

INTRODUCTION:

Learners must have been introduced to machines and covered the following subtopics; Work, Energy Power, Force (effort, load), Mechanical Advantage (MA) and Velocity Ratio (VR).

Machines are devices that make work easier though not smaller. This is achieved by the application of a force (effort) at one point in order to overcome another (load) at another point.

People and machines cannot do work without a supply of energy. We get energy from the food that we eat. Machines are fed with energy in many other forms e.g. fuels such as coal, oil and gas, solar energy, hydro electricity, nuclear energy etc.

A machine converts the energy supplied into another form. The total amount of energy input the machine is equal to the total amount of energy output. This implies that a machine doesn’t consume energy; however the useful energy or work done is usually less than the total energy input.

The amount of time taken to do a piece of work may vary from machine to machine depending on how powerful the machine is. A faster machine uses more power in doing a piece of work.

ACTIVITY 1:

The teacher will guide the class in reviewing the previously taught areas that relate to machines. Review the following;

• Work, Energy, Power, Force, MA and VR.
• Examples of simple machines
  • Levers
  • Pulleys
  • Inclined plane
  • Hydraulic machine
  • Petro engines.

ACTIVITY 2:

The teacher organizes the class into groups of 5 to 10. Each group will carry out the following assignments.

Record examples of commonly used machines in the following categories;

1. Levers

Machine	Note where the pivot is found	Identify the class of lever
Wheel barrow
Human fore arm
Bottle Opener
Pair of Scissors
Pair of pliers

2. Pulleys

Draw diagrams to show the following pulley systems

• Single fixed
• Single moving
• Block and tackle system of VR=4

3. The inclined plane. A slope or ramp which allows a load to be raised more gradually and by using a smaller force (effort) than if it was lifted vertically upwards.

As we climb up a stair case we use the principle of the inclined plane.

h

Find the formula for the work input and the useful work output.

ACTIVITY 3:

Efficiency = =××100%

=MA××100%

PRACTICAL EXERCISE OF MEASURING THE MA AND EFFICINCY OF A BLOCK AND TACKLE PULLEY SYSTEM AND SHOWING THE VARIATION OF MA WITH LOAD AND EFFICIENCY WITH LOAD

INSTRUCTIONS

1. Assemble the block and tackle system as shown in the diagram above.
2. Suspend known masses between 1.0kg to 6.0kg on the system in turn and record readings of the spring balance for the effort needed to just raise the loads.
3. Work out the MA and efficiency for each load.
4. Record your readings in the table below.

Mass/kg	Load/N	Effort/N	MA=Load/effort	Efficiency
1.0
2.0
3.0
4.0
5.0
6.0

5. Plot graphs of MA against load and efficiency against load.
6. What deductions can you make from the graphs?

ACTIVITY 4

Mr. Kapere is not keen at taking his car for service when the mileage is due. He has always reasoned that “after all the car still moves perfectly well.” In a small note to kapere, advise him as a friend on the disadvantages of continual use of the car without servicing it.

• List down as many causes of inefficiency in machines and state how they can be minimized.
• Prepare a group’s presentation to the whole class.

• inary level Physics by AF Abbott

PHYSICS

SAMPLE LESSON PLAN

DATE	CLASS	SUBJECT	NO.OF LEARNERS	DURATION	TIME
…./…./…	SENIOR THREE	PHYSICS	50	80 MINS	8.00 – 9.20am

Topic: Machines

Subtopic: Efficiency

Time: 80 minutes

Objectives: by the end of this lesson, learners should be able to:

• Define work input, work output, velocity ratio, mechanical advantage and efficiency.
• Derive the relationship between Efficiency, velocity ratio and mechanical advantage.
• Identify the causes of inefficiency in a simple machine such as a pulley system.

Teaching aids:

• Pulleys and pulley strings
• Loads (masses of 100g)
• Inclined plane
• Spring balance

References:

• The world of Physics by John Avison
• Ordinary level Physics by AF Abbott

Time/Minutes	Teacher’s activity	Learners’ activity	Comments
10	Introduces lesson by defining work, energy and power. Finds out what Learners know about work and different types of energy.	Suggest different forms of energy and its transformations from one form to another.
20	Introduces mechanical advantage as the ratio of load to effort Velocity ratio as the ratio of distance moved by effort to that moved by load in the same time. Simple illustrations in form of calculations	May ask questions for clarity Try out the numeric questions given by teacher
15	Shows class how simple pulleys of different velocity ratios may be assembled (demonstration) Asks learners for any observations and conclusions made Responds to learners’ queries.	Make observations and draw conclusions Reactions Make notes
35	The inclined plane. Use of spring balance to find effort that pulls load up the incline. Organizes class into groups and provides necessary apparatus for inclined plane.	Measurement of effort, load, distance by effort and distance covered by load. Calculation of Work input, work output and efficiency for different loads. (group work) Relationship between efficiency and load(graph) Relationship between MA and load.
5	Supplements learners’ observation and conclusions Concludes lesson.

Lesson Evaluation:

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Heat Transfer

TEACHERS’ GUIDE

SUBJECT : PHYSICS

TOPIC : HEAT

SUB-TOPIC : Heat transfer

CLASS : Senior One

CLASS SIZE : 60 Students

TIME REQUIRED : Minimum: 240-360 minutes

Brief description of the unit

This unit discusses the types of heat transfer, the factors that affect the rate of heat transfer as well as applications of heat transfer. Heat is a form of energy that produces a sensation of warmth when absorbed by our bodies. Heat energy is the commonest form of energy in applications by humans and other living things. Heat energy is used for preparing food, keeping us warm, drying clothes, etc. Almost all forms of energy finally degrade to heat.

Unlike electricity, heat energy leaks easily. There is therefore need to study the ways heat energy is transferred with the aim of conserving it, using it economically so as to reduce global warming.

Main Content to emphasise

Heat transfer by conduction, convection and radiation.

Objectives

By the end of the topic, the learners should be able to:

1. Define thermal conduction, convection and radiation.
2. Arrange Iron, copper, Aluminium and glass in order of their thermal conductivities.
3. Describe the mechanism of thermal conduction in terms of the simple kinetic theory.
4. Explain the applications of good and poor conductors of heat.
5. Illustrate the process of thermal radiation.
6. Discuss the factors that determine the rate of thermal radiation.
7. Demonstrate practical applications of good and poor thermal radiators.
8. Explain the process of thermal convection.
9. Describe practical applications of thermal convection.
10. Identify situations where energy can be conserved through good usage of factors affecting thermal transfer.
11. Compare the efficiency of different types of charcoal stoves with reference to heat transfer.

Methods

Group work

The class should be divided into groups of 5 – 10 with each group having a secretary and a chairperson.

Teaching / learning aids

Source of heat and tripod stand; Iron, copper, aluminium and glass rods of the same length and diameter; Wax; Stop clock

Job related life skills

In forming the groups and during the activities, ensure that the following job-related life skills are deliberately achieved.

• Personal attributes: - behave appropriately, punctuality, reliability, self confidence, seek advice, show tenacity and motivation, be analytical and imaginative.
• Communication: - ability to read, write, listen, and speak in appropriate ways for different audiences. Know and apply general and specialized vocabulary.
• Team work: - ability to cooperate and share tasks with colleagues.
• Problem solving: - goal focused, seek out relevant information, identify constraints, evaluate alternatives and make decisions/ choices.
• Implementation and application: - the ability to carry out complex operations and follow instructions to achieve accurate results.
• Application of number: - ability to work with and present numerical data, using appropriate intermediate calculations.
• Information skills: - ability to present evidence to meet the needs of different audiences using graphs, reports and images.

Activity one

Comparing the rates of heat transfer by conduction in different materials.

Ask the learners should do the following:

• Place one end of each rod in the flame of a candle or a Bunsen burner, while holding the other end.
• Describe the mechanism by which heat travels along the rod to their hands.
• Measure and record the length of time it takes the heat to reach their hands through the rod.
• Describe a better way of comparing the rates of thermal conduction of the different materials, using the apparatus given or any other that is available.
• Carry out the experiment and arrange the materials in order of their conductivities by attaching three pieces of wax at equal intervals on each rod and then simultaneously heating the ends of the rods in a flame.

	Time taken for the 1st piece of wax to fall off	Time taken for the 2nd piece of wax to fall off	Time taken for the 3rd piece of wax to fall off	Ranking in order conductivity(best No. 1)
Copper
Iron
Aluminium
Glass

NB

The rods should be long enough to get measurable time differences.

Ask the learners to discuss the applications of good conductors and poor conductors.

Activity Two

Heat transfer by convection.

Round bottom flask, heat source, potassium permanganate, glass tube.

Ask the learners to do the following;

• Fill the flask with water and carefully drop grains of potassium permanganate at the bottom of the flask using the glass tube.
• Apply a gentle flame at the bottom of the flask and observe.
• Describe and explain the observations.
• Discuss how convection takes place in gases.
• Discuss how convection is applied in house ventilation. Explain the value of good ventilation to comfortable living.

Activity Three

Heat transfer by radiation.

Teaching / learning aids

Hot water, cubic metal container, or Leslie cube, thermometers, kitchen foil, source of heat (radiant coil, filament bulb, or candle).

Ask the learners to do the following;

• Place their hands at a safe distance above, below and at the side of a source of radiant heat and describe the mechanism by which heat reaches their hands in each of the positions.
• Fill the metal cube with hot water and feel the heat at a distance from each side of the cube.
• Describe and explain the difference in the amount of heat felt on each side of the cube.
• Suggest better ways of comparing the rates of thermal radiation from the different surfaces.
• Carry out an experiment to compare the rate of radiation of heat by different surfaces.

One possible experiment is by holding a thermometer with a blackened bulb (placed centrally) at distance from a surface of the Leslie cube containing hot water and recording the temperature readings at regular time intervals. This is repeated for the different types of surfaces of the cube.

	Temperature in oC recorded by thermometer at 30 second intervals
	30	60	90	120	150	180	210	240	270	300
Dull surface side of the cube
Shiny surface side of the cube
White surface side of the cube
Black surface side of the cube

Plot the graph of temperature against time for the different surfaces on the same axes. Use computer spreadsheets where possible.

Comment on the graphs.

1. Discuss the type of finishing you would recommend for each of the following:

a. The inside walls of a bedroom of a house in a hot area.

b. The outside wall surface of a house in a hot area.

c. The inside walls of a bedroom of a house in a cold area.

d. The wall surface of a house in a cold area.

2. Discuss the economic implications of the choice of colours when finishing a house.

Experiment on rates of absorption of heat.

Learners are given a shiny polished pan with a cover that has a hole for a thermometer and a similar pan that is all blackened. The two pans are put out in the hot sun. Temperatures of the water are taken every minute for ten minutes.

The results are recorded in a table.

	Temperature in oC recorded by thermometer at time intervals in minutes
	1	2	3	4	5	6	7	8	9	10
Dull surface pan
Shiny surface pan

Plot the graph of temperature against time for the two surfaces on the same axes. Use computer spreadsheets where possible.

Comment on the graphs.

The learners should discuss the applications of good / poor radiators and absorbers in the home, in dressing, in vehicles, etc.

With reference to conservation of energy, the learners describe one situation where it is necessary to reduce the rate of heat transfer so that energy is conserved (economised).

With reference to conservation of energy the learners describe a situation where it is necessary to enhance the rate of heat transfer so as to conserve (economise) energy.

Activity Four

1. Groups should carry out a project on one of the following

• Keeping cooked food warm for a long time using local materials.
• Firing bricks more effectively.
• An energy saving charcoal stove.

2. The groups present their essays to the class.

Links

http://en.wikipedia.org/wiki/Thermal_radiation

http://en.wikipedia.org/wiki/Solar_hot_water

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm

Requests

Pictures of a vacuum flask, green house, domestic solar water heater.

Exercise

1. Describe an experiment to show that black surfaces are better absorbers of heat than shiny surfaces.

2. The diagram below shows two cubes of the same dimensions A is black while B is shiny. The cubes are both filled with cold water. A source of heat is placed mid-way between the cubes.

Explain what is observed on the thermometers.

3. Explain why the sea remains cooler during day and warmer during night.

4. State any two factors on which the rate of heat transfer along the length of a metal bar depends.

5. Distinguish between conduction and convection.

6. Distinguish between convection and radiation.

7. What factors affect the rate of heat radiation from a surface?

8. Explain how convection determines ventilation of a house.

9. Use the kinetic theory of matter to distinguish between poor conductors and good conductors of heat.

Scheme of work

Sub-topic	Periods	Specific objectives	Content	Teaching and learning strategies	Notes
Conduction	6	Define conduction. List the factors affecting the rate of conduction. Carry out experiments to compare good and bad conductors. Carry out experiments to show that water is a poor conductor of heat. Explain applications of conduction.	Concept of conduction. Factors affecting the rate of conduction in solids. Compare conductors and insulators. Water as a poor conductor of heat. Applications of conduction.	Learners carry out experiments to compare good and bad conductors. Discuss applications of good and bad conductors	Application treated qualitatively eg vacuum flask, flat iron and insulation. Rate of conduction treated qualitatively using simple experiments.
Convection	6	Define convection. Describe how convection current is formed. Experimentally demonstrate convection current. Describe applications of convection.	Concept of convection. The convection current. Applications of convection	Experiments to show convection.	Applications eg in the domestic hot water system, land and sea breezes, ventilation and car radiators.
Radiation	7	Define radiation. Carry out experiments to compare radiators and absorbers. Explain the application of radiation of heat. Describe how solar energy can be trapped and used in a water heating system.	Concept of radiation. Factors affecting radiation (or absorption). Comparing radiators(emitters) and absorbers. Application of radiation. Green house effect. Solar heating system.	Experiments with good and bad absorber (or radiators). Discuss how conduction, convection and radiation considerations are applied in the vacuum flask.	Effect of nature of surface on absorption and emission of radiation.

Sample lesson plan

Class: Senior one.

Subject: Physics

Topic: heat.

Sub topic: transfer by conduction.

Time: 80min

Number of learners: 40 - 80

Objectives: to define conduction, carry out experiments to compare good and poor conductors.

Method:

Group Work and experiments

Teaching aids:

Source of heat and tripod stand; Iron, copper, Aluminium and glass rods of the same length and diameter; Wax; Stop clock.

Time	Theme	Teachers activity	Learners’ activity
5min	Review	Review work done on temperature and thermometers	Answer question on temperature and thermometers.
15min	Rates of thermal conduction.	Provide apparatus and give instructions for experiment to compare rates of conduction	Carry out experiment to compare rates of conduction.
20min	“	Guide learners to present results and discuss them.	Present their results to class and class discusses the results
15min	Applications of thermal conduction	Gives instructions and supervises.	Discuss applications of conduction in groups
20min	“	Guides the discussions	Present results of their discussions of applications of conduction to the class.
5min	“	Give assignment on domestic applications of conduction.	Take assignment.

Exercises:

1. Describe an experiment to show that black surfaces are better absorbers of heat than shiny surfaces.

2. The diagram below shows two cubes of the same dimensions A is black while B is shiny. The cubes are both filled with cold water. A source of heat is placed mid-way between the cubes.

Describe and explain what is observed on the thermometers.

3. Explain why the sea remains cooler during day and warmer during night.

4. State any two factors on which the rate of heat transfer along the length of a metal bar depends.

5. Distinguish between conduction and convection.

6. Distinguish between convection and radiation.

7. What factors affect the rate of heat radiation from a surface?

8. Explain how convection helps in ventilation of a house.

9. Use the kinetic theory of matter to distinguish between poor conductors and good conductors of heat.