Question: how do your eyes differentiate between colours when there are a lot?

Rosie Cane answered on 18 Jun 2017:

Interesting question! We see colour because of cells in our eyes called ‘cones’. If you have a few differently coloured objects – say a green apple, a red strawberry and a yellow banana – these objects absorb (take in) some of the light that shines on them and reflect the rest to the cones in your eyes.

To understand this better we need to look at a term called ‘wavelength’. You see, one of the characteristics of light is that it behaves like a wave! The wavelength is the distance between two peaks (the highest points) of a wave. This can be tricky to understand but here’s a really useful website to help: http://www.ducksters.com/science/light_spectrum.php.

Different colours have different wavelengths that give them their specific colour. Which wavelengths are reflected or absorbed depend on the properties of each individual object, no matter how many other colours are around it.

So when light shines on the apple, wavelengths of about 510 nanometres (0.00000051 metres) bounce back to our eyes. These are the wavelengths of green light. For the strawberry, it will be wavelengths of about 650 nanometres (red light) that bounce back and for the banana it will be about 570 nanometres (yellow light).