Dispersion of Light (Cambridge International IGCSE Physics)

Spec point — 3.2.9 · Describe the dispersion of light as illustrated by the refraction of white light by a glass prism

Dispersion of light

• The dispersion of light is illustrated by the refraction of white light by a glass prism

• White light contains the wavelengths 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 glass 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 is separated into colours by passing it through a triangular prism

The visible spectrum of light

Spec point — 3.2.9 · Know the traditional seven colours of the visible spectrum in order of frequency and in order of wavelength

• Visible light is the only part of the spectrum detectable by the human eye

  • In the natural world, many animals, such as birds, bees and certain fish, can perceive beyond visible light and can see infra-red and UV wavelengths of light

• The seven different colours of visible light waves correspond to different wavelengths

• In order of longest wavelength and lowest frequency to shortest wavelength and highest frequency:

  • red
  • orange
  • yellow
  • green
  • blue
  • indigo
  • violet

The dispersion of light creates the seven colours of the visible spectrum: red has the longest wavelength; violet has the shortest

Exam Hint To remember the colours of the visible spectrum you could remember either:

• the name “Roy G. Biv”
• the saying “Richard Of York Gave Battle In Vain”

Monochromatic light

Spec point — 3.2.9 · Recall that visible light of a single frequency is described as monochromatic

Extended Tier Only

• A visible light source of a single frequency (a single colour) is monochromatic
• A laser beam is monochromatic because it emits a single colour of light

The laser emits monochromatic green light