Physics Grade 12

Unit 5: Waves

Note 7: Colour and Wavelength


Reference: Chapter 9.6


Knowing that red light has a longer wavelength than blue light, which do you think has a greater separation of nodal lines?

See page 476 and notice red light has a greater separation of nodal lines than blue light.  This is because red light has a longer wavelength.

Recall that:  


In some media (Dispersive media) the velocity is dependent on the wavelength of the light (i.e. a prism). White light is made up of all colours. If white light passes through a prism, its different frequencies are refracted (bent by different amounts) and we have dispersion. Shorter wavelengths (higher frequencies) are refracted more than longer wavelengths.

The prism's glass has a different index of refraction for each colour and therefore different colours travel at slightly different speeds in the glass.

Recall :



Page 478 # 5,6

Page 479 #4-6