Does light have colour?
Try creating spectrums of colour using marbles, glass beads, bits of glass, gems, such as those in a ring, different prisms, etc. Do you always get the same band of colour?
Experiment with soap bubbles or a fine coat of oil (vegetable oil) on a water surface. Do you get a spectrum of colour?
Experiment with coloured glass. Do the results change? If you can get bits of coloured glass from someone who does stained glass work, experiment with how different colours affect the spectrum of light. What happens if you use two colours of glass at one time? [Even the plastic overhead mathematics manipulatives will allow for experimentation with colour and light.]
Extend this activity into art and experiment with the mixing of colours of paint. Start with primary colours--red, yellow and blue. Mix pairs of these colours. Record results. Experiment with shades of colour by using more of one colour and less of another; and make use of white and black to lighten and darken shades of colours. Encourage discussion and sharing. Record findings.
Sky colours during the day, at sunrise and sunset, depend on particles in the air and the distance light is travelling. Try this experiment. Measure a cup of water (250 ml) into a clear glass. Use a flashlight in a slightly darkened room to shine light from the side, behind, etc. onto the glass. Now stir into the water a quarter teaspoon of milk to simulate pollution and dust particles in the air. Again use the flashlight to shine a beam of light from the side, back, etc. What do you observe? Discuss and record. (From the side the milk particles should scatter the blue part of the light; from the back the orange and pink colours should be scattered. When the sun is close we see blue skies; when it is further away we get coloured sunrises and sunsets.) This activity is adapted from Primary Science by Hartman, 1994.
Colours in Light
Using prisms in a darkened room allow only a small beam of sunlight to shine on the prism. Locate the band of colours on the wall. What colours do you see? If you have different colours of glass available (coloured sunglasses or pieces of cellophane will work), look through each of the different colours of glass at your colour spectrum. What do you observe? Why?
Ask students to do some research, if necessary, to obtain satisfying answers. If you have the primary colours of light (red, green, blue) in pieces of cellophane, overlay corners of each to create secondary colours. Discuss the results. What colour do you get when all three colours are together? Use two (or three) flashlights and primary coloured cellophane pieces to experiment with combining colours. Predict results before you do the experiment. Cover the ends of the flashlights with red and blue cellophane. Shine them individually first and later together so that the light is on the same piece of white paper. What colour do you see? Repeat with red and green? blue and green? Are the combined colours of light the same as the combined colours with paint? Discuss. Record results. If you have other colours of cellophane, experiment by combining other colours. Are you able to create white?
Use a projector and petri dishes with water and added food colouring so that dishes may be stacked to experiment with colours and light. Have students predict results prior to use of various colours or combinations of colours.
Use a projector to create shadows of objects. Observe the shadows as the object is placed close to the light source and farther away. Discuss findings.
Light travels in straight lines. Use three index cards folded in half so that they will stand upright. In the centre of each (through both layers) punch a hole. Line up the cards so that a beam of light from a flashlight may be shone through the holes onto another card without a hole. Move one card slightly aside. Will the light still pass through all the holes? Discuss.
Light Rays can be Bent. (Refraction)
Place a pencil in a glass of water. Observe the pencil from different angles. What do you observe? Fill an aquarium or a clear rectangular container with water. Experiment with putting objects in the water (coin, rod, floating object, etc.). Look at these objects from straight above, from the side, from an angle, or from beneath if possible. Predict what you will see? What observations can you make? Cover the front of a flashlight with several layers of masking tape. Poke a hole near the centre of the tape to allow a thin beam of light to shine through. Darken the room. Focus the light straight down into the water, at an angle, from the side, etc. What do you see? Does what you see change if you observe from a different angle?
Create a "light bender" with a shoebox, a square jar of water, and a flashlight. Make a slit in one end of the shoebox through which to shine the light in a slightly darkened room. Set the square jar of water in the centre of the box. What happens to the beam of light? Discuss.
