One of the most important experiments on light was made by Isaac Newton. He was the greatest of all English men of science. He discovered that sunshine (white light) is made up of many colours. Over 300 years ago, Sir Isaac Newton passed a beam of white light through a prism. A prism is a triangular piece of glass, which allows light to spread out into a band of six colors. These colors are red, orange, yellow, green, blue and violet. Newton then sent this light through a second prism where the light became white once again.

What did Sir Isaac Newton do?
He first took the white light apart and then he put it back together again.

The most common example of a spectrum is the rainbow created in nature. The rainbow is caused by sunshine (white light) shining on water droplets that are in the air just after a summer shower. Thousands of these water droplets break up the light, just like Sir Isaac Newton’s prism. Can you make a rainbow? Of course! Make your own rainbow by turning on the garden hose, which has a nozzle that will make a fine mist, or spray. Make sure the sunlight is coming over your shoulder. You have made a rainbow.

If light is white and all we see is light why do things appear different colours?
Objects absorb some of the colours in the white light and then reflects the rest. The colours that are reflected provide the colour of a specific object. Think about these three basic colours (Red, Blue, Green), if an object absorbs green but reflects blue and red then the object will be purple. The mix of blue and red light gives us purple.

Did you know?
The computer screen you are looking at now can only produce three colours – Red, Blue and Green. So how do we see white on the screen? It follows Newton’s experiments on light and puts the three colours all together to create white.

EXPERIMENT TO TRY

Colour Wheel

  1. Print out this template (you need a PDF reader like the one from Adobe).
  2. Cut out the discs and then put a toothpick, or pencil, through the centre. You may need to fix the disc with a bit of sticky tape.
  3. Spin the wheel and have a look at the colours that are created. Look at the outer ring of the first disc shown above and the colour should disappear.
  4. Repeat with the other patterns and colours.

Note: You may need to stick the paper on to cardboard if your paper is too thin.

Can you colour your own wheel so that when it spins all the colours disappear? (Bring it to school for $500 reward money)

Fun Facts about Light

We do not know of anything in our universe that travels faster than light. The sunlight we see today left the sun 93 million miles away to reach us about 10 minutes later. Light from stars farther away may have taken billions of years to reach our eyes. How many times can light travel around the world while you are saying your name? ……………..more than four times.