Definition of Dispersion
Dispersion is the
separation of white
light into a spectrum
by the process of
The cause of dispersion
• Dispersion occurs because different colours
of light travel at slightly different speeds
through transparent substances.
• In glass, perspex and water red travels
quickest, violet slowest.
Here is a glass
A ray of white light arrives
It is (mainly) reflected or refracted ?
away from or towards
the normal the normal
What happens to the ray of light?
But different colours are refracted by
In fact, the ray is :
• (bent through an angle), anddevi ated
• dispersed (split up into separate colours)
What happens now?
Red is deviated most / least ?
Violet is deviated most / least ?
There is a spectrum
on the screen:
Red Orange Yellow Green Blue Indigo Violet
ROY G BIV
What is the real difference
between red and violet light ?
An example of dispersion
caused by water