Investigating colours in sunlight - middle and senior classes

By the end of fourth class children should know that white light can be split into a range of colours, known as a spectrum. The children can use a slide projector and prism to cast a large spectrum on a wall. They can identify the colours and the order in which they appear on white paper or the screen. Other ways for children to see the spectrum are

  • To place a plastic ruler in the sunlight and watch the spectrum as it appears on the ceiling or wall
  • To blow bubbles
  • To place a mirror in a shallow container of water in sunlight

The white rays of sunlight fall on drops of rain, which act in a similar way as the prism to form a rainbow. Children can experiment to make a rainbow.

Mixing coloured light

The children should try mixing the primary colours of light. Three torches should be covered with red, blue and green filters and shone onto a white screen or piece of paper. The children will observe that different colour combinations occur. Green and blue light will combine to make cyan (bluegreen); blue and red light make magenta (purple-red); and green and red light make yellow. Together the red, blue and green light beams should give white light, but only if the colours are pure and are projected at the same intensity. The process of mixing the primary colours of paint is different from mixing the primary colours of light; colour paints have a different set of primary colours.

Children should investigate what happens when they look at flowers, crayons and other coloured objects through different-coloured filters, and should record the results.