Light

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Teaching Outlines

1. Light is a form of energy
2. Light travels as electromagnetic radiation; with waves of different wavelengths
3. Light interacts with material particles in discrete packets called photons
4. Different wavelengths are associated with photons of different energies

Concept #1 - Light is a form of energy

Learning objectives

1. Light is a form of energy and travels as electro-magnetic radiation. There are other radiations apart from light that travel as electro-magnetic radiation.
2. It is possible to look at light and other electro magnetic radiation as a wave or as a particle known as the photon.

Notes for teachers

These are short notes that the teacher wants to share about the concept, any locally relevant information, specific instructions on what kind of methodology used and common misconceptions/mistakes.

1. Light is a form of energy that is transported as electromagnetic radiation but interacts with material particles as discrete packets of energy that are called photons.
2. Sun provides us with heat and light. This travels through the near vacuum of space. So there is no material to transport energy. #When we block light we also block the heat radiation. Any source of heat also radiates some visible light.
   
3. This radiation can be thought of as waves of different wavelengths. The waves are not of material objects but travelling waves changing electric and magnetic fields. Different wavelengths are associated with different energy levels and different kind of radiation.

Click here for more notes on the nature of light, visible light and colours.

The following video is useful to see the development of theories of light.	Listen to Richard Feynman, renowned physicist talk about the nature of light.
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Activity No # 1 - Thought Experiment - Radiation from the Sun

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• Estimated Time - 30 minutes
• Materials/ Resources needed - None
• Prerequisites/Instructions, if any - None
• Multimedia resources

This is a video that explains radiation as an animation. Use this to initiate the discussion and talk about the questions below.

• Website interactives/ links/ simulations
• Process (How to do the activity)

1. Heat a piece of iron and watch the iron changes colour.
2. Keep a black cloth under light and feel it after some time
3. If possible, demonstrate/ discuss what happens in a glass house
4. Show the video and discuss the questions below, alongwith the observations above

• Developmental Questions (What discussion questions)

From all this can we see the following:

1. What happens to the energy from the sun? - Energy is transported from a source to a destination without a medium
2. Are there different kinds of energy/ forms of energy? - The energy is of different kinds – heat, light of different colours, X ray, eyc.
3. What happened here when you places something in the sun? - One form of the energy can get converted to another. They must therefore have things in common - radiant heat and light are similar in many ways and different in some ways.
   
4. When we heated the iron what changes did we see? Why did the colour change? (From a dull grey to red to yellow to white when light of all wavelengths are radiated in addition to the heat.)
5. On a cold day the temperature inside a glass house is much higher – why? Because light of a shorter wavelength can travel through glass and is absorbed by the ground and plants. The ground reflects back radiation of a higher wavelength – infra-red and heat radiation. This cannot pass through glass and so the glass house is much warmer.
6. Explain that studies done on how light travels has helped us visualise it now as changing electrical magnetic fields that interact with other material objects as packets of energy.

• Evaluation (Questions for assessment of the child)
• Question Corner

Activity No # 2 Black is Hot - White is Cool!

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At the end of this experiment children should be able to recognize that black objects absorb more radiant energy than white objects. This is a simple experiment that can be done in the classroom or at home. Children should report their findings in a formal way – this is to help them formalise their understanding:

• Estimated Time - 25 minutes
• Materials/ Resources needed

One piece of black cloth. A similar sized white cloth. Ideally the two materials should be the same and texture. It may not be very critical if they are not. Cloth pieces of other colours but similar material and texture.

• Prerequisites/Instructions, if any - None
• Multimedia resources - None
• Website interactives/ links/ simulations
• Process (How to do the activity)

1. Leave the two pieces of cloth out in direct sunlight for about 15 minutes.
2. At the end of the period feel the clothes.
3. Try this with other coloured clothes
4. Observations written in an organized format - aim of the experiment, method and questions below are to be answered in the observation

• Developmental Questions (What discussion questions)

1. Which seemed warmer the black or the white cloth?
2. If you used other coloured clothes, arrange them in ascending order of warmth.

Which is warmer – the dark cloth or the light cloth?

• Evaluation (Questions for assessment of the child)
• Question Corner

Concept #2 Light and Colours

Learning objectives

1. Light is a form of energy.
2. The different types of photons are seen by us as different colours.
3. There are some kinds of photons that we cannot see – for example heat radiation, X rays, infra-red and ultra-violet rays. We say that light travels as a wave and different coloured lights have different wave-length associated with them.

Notes for teachers

These are short notes that the teacher wants to share about the concept, any locally relevant information, specific instructions on what kind of methodology used and common misconceptions/mistakes.

Activity No #

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• Estimated Time
• Materials/ Resources needed
• Prerequisites/Instructions, if any
• Multimedia resources
• Website interactives/ links/ simulations
• Process (How to do the activity)
• Developmental Questions (What discussion questions)
• Evaluation (Questions for assessment of the child)
• Question Corner

Activity No #

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• Estimated Time
• Materials/ Resources needed
• Prerequisites/Instructions, if any
• Multimedia resources
• Website interactives/ links/ simulations
• Process (How to do the activity)
• Developmental Questions (What discussion questions)
• Evaluation (Questions for assessment of the child)
• Question Corner

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