Colour & Reflection of Light (AQA GCSE Physics)

• White light is a mixture of all the colours of the spectrum
• Each colour has a different wavelength (and frequency), making up a very narrow part of the electromagnetic spectrum
• White light may be separated into all its colours by passing it through a prism
  • This is done by refraction
  • Violet light is refracted the most, whilst red light is refracted the least
  • This splits up the colours to form a spectrum

• This process is similar to how a rainbow is created

White light may be separated into all its colours by passing it through a prism

Colour Filters

• Colour filters work by absorbing certain wavelengths and transmitting other wavelengths
  • These certain wavelengths correspond to certain colours

• When white light passes through a coloured filter, some colours are absorbed whilst others are able to pass straight through
• For example, when white light passes through a red filter:
  • Red light is transmitted
  • All the other colours are absorbed

• The colour that is transmitted is the same colour as the filter

A red filter transmits only red light and absorbs all other colours of light

• The colour of an opaque object is determined by which wavelengths of light are more strongly reflected
• Wavelengths that are not reflected are absorbed
  • Hence, this is why different objects appear to be different colours

• For example, white light upon a green surface will only have green light reflected and the others absorbed
  • This light is reflected into our eyes to see the surface in that colour

A green surface reflects green light and absorbs all other colours

• An object will appear white if:
  • All wavelengths are reflected equally

• An object will appear black if:
  • All wavelengths are absorbed

• An object will appear transparent if:
  • All the light is transmitted, and only a small amount is reflected or absorbed