Students generally do not intuitively recognise white light is a mixture of colours of light

Light, Sound and Waves


Resources to Address This

  • A spectrum of colours: the dispersion of light  (11-14)

    Ref - SPT Li04 PN01

    With the triangular block, the geometry of the prism is such that there is some separation of the different colours of light at the first face and then further separation at the second.

    As a result the red light lands at a different point on the screen to the violet light and in between we can see the full spectrum of colours. The white light is dispersed into its constituent colours and the process is therefore referred to as dispersion.

    View Resource
  • A simple spectrum (11-16)

    Ref - Practical Physics; Light and optics; Spectra and colour; 

    This should be as simple as possible, without complicated optics, as an introductory experiment.

    The spectrum will be the most pure if the screen is held at the same optical distance from the lens as the image was before the prism was inserted, and the prism is turned to minimum deviation. However, turning the prism to a greater deviation will show a wider spectrum.

    View Resource


The following studies have documented this misconception:

  • Grusche, S. () Students’ ideas about prismatic images: teaching experiments for an image-based approach. International Journal of Science Education,

    Review sheet

  • Haagen-Schützenhöfer, C. () Students’ conceptions on white light and implications for teaching and learning about colour. Physics Education, 52.

    Review sheet

  • Eaton, J., Anderson, C.W. and Smith, E.L. () Students' misconceptions interfere with learning: case studies of fifth-grade students. Research Series 128, The Institute for Research on Teaching, Michigan State University.

    Review sheet

Limit Less Campaign

Support our manifesto for change

The IOP wants to support young people to fulfil their potential by doing physics. Please sign the manifesto today so that we can show our politicians there is widespread support for improving equity and inclusion across the education sector.

Sign today