1. Projecting the Light - ReflectionIn this activity you will try to find out which is the best way to make a light visible given a fixed light source.
You will need:
- candle* or light bulb, holder and battery
- 3 flat mirrors in holders
- curved reflector or cardboard and aluminium foil
Work with a partner, if possible in a darkened room. Place the light source on a table or bench. The partner should sit at least 1m away and note down how bright the source appears.
Now place a flat mirror behind the light source and note the difference in brightness.
Use the other two flat mirrors in various positions, repeat the observations and note them down.
Replace the flat mirrors by a curved reflector and, again, repeat the observations. Try bending the reflector into different shapes (drawing the shapes into your results table) and repeat. Which arrangement gives the brightest light? See if you agree with your partner by swapping roles.
2. Projecting the Light - RefractionIn this activity you will try to find out what happens when light passes from air into water, glass or perspex.
You will need:
- 250ml beaker
- cooking oil
- raybox (with 3 slits) and power supply
- Place a pencil or pen in the beaker. Half fill the beaker with water. Stand back from the beaker.
What has happened to the pen / pencil? Draw what it looks like now.
The pen or pencil appears to bend or split because light refracts (changes direction) as it passes from the water into air.
- Remove the pen or pencil. Set up the raybox and place the beaker of
water in front of the light coming from the three slits.
What happens to the light? Make a drawing.
The beaker acts as a convex lens, which converges the light.
Empty out the water and half fill the beaker with cooking oil. Look carefully at the light rays. Make a second drawing. You should have noticed that they come to a point (the focus) closer to the beaker.
This is because the oil refracts light more than water.
- Replace the beaker with the prism. The light refracts. You may even be able to see a spectrum.
What would happen, do you think, if you placed a second prism upside down under the first and directed a second set of rays into the bottom prism? If possible you may be able to do this with another pupil, or your teacher may be able to demonstrate this arrangement.
The two prisms behave like the beaker, that is, like a convex lens.
3. Solar PowerIn this activity you will try to transfer solar energy into heat energy.
You will need:
- solar panel
- 250ml beaker or other container
- 0-1000C thermometer
Allow the water to flow through the panel for at least 30 minutes. Measure the temperature of the water that is collected. It should be higher than the temperature of the cold water!
Solar panels like this are used on the roofs of buildings (even in the UK) to provide hot water.
If you haven't got access to a solar panel try these activities:
- See how much light is needed for a solar-powered calculator to work. Shine a lamp on the calculator and cover up the solar cell with 1 sheet of paper. Add more sheets until the calculator switches off. Compare your result with a different calculator.
- Solar energy is only one of many different forms of renewable energy. What is meant by 'renewable'? Name and describe two other forms of renewable energy.
4. SatellitesAnswer the following questions:
- What is the name of the force that keeps satellites in orbit?
- There are many artificial satellites. What is the name of the natural satellite in orbit around the Earth?
- Find out the names of some artificial satellites currently in orbit.
- Signals from a satellite travel at the speed of light, 300 million metres every second. If it takes 0.1 seconds for a signal to be received on Earth, how far, in kilometres, is the satellite from the Earth?
- What does GPS stand for? What is the purpose of GPS?
- Satellites have, for many years, used solar energy to provide them with power.
How do you think that they do this? Make a drawing to illustrate your idea.
What do you think are the advantages of using solar energy compared with any other form of energy to power the satellites?