Project: The colour of light

This section looks at the way we see colour. What makes light visible and the others (radio-waves, x-rays, radar and light - electromagnetic radiation) is not simply the sensitivity of our eyes. As wavelengths get shorter the colour changes, from deep red, shorter again and we see orange, shorter still we see yellow, then green, then blue then violet. After violet, the radiation becomes invisible once more - it is ultraviolet.

Also reviewed is how we see brightness and how light becomes colour. When the sun sets, which depends on the weather, as the sun gets lower in the sky it becomes yellow, a little lower, orange and the best sunsets have a red sun by the time it reaches the horizon. The particles in the atmosphere scatter some of the light, shorter blue wavelengths are scattered more easily, leaving longer orange/reddish ones visible, this also makes the sky away from the sun look blue. In the shade on a sunny day, the light comes from the blue part of the sky.

In photography the 'colour temperature scale' principles are used. The temperature is measured in Kelvins, similar to Celsius but starting at the lowest possible temperature.