A beam of light consisting of red, green and blue colours is incident on a right angled prism. The refractive index of the material of the prism for the above red, green and blue wavelengths are 1.39, 1.44 and 1.47, respectively.
The prism will:
separate all the three colours from one another
not separate the three colours at all
separate the red colour part from the green and blue colours
separate the blue colour part from the red and green colours
As we learnt in
Critical angle -
= Refractive index of rarer medium / Refractive index of denser medium
- wherein
When angle of incidence of a travelling from a dence medium to rarer medium is greater than critical angle, no refraction occurs.
angle of incidence at surface AC=
Critical Angle of incidence
For red
For green
For blue
Since refractive index of green and blue is greater than and hence their critical angles are less than
So green and blue will be completely reflected while red will emerge out of prism. Hence red will be separated from green and blue.
Option 1)
separate all the three colours from one another
Option 2)
not separate the three colours at all
Option 3)
separate the red colour part from the green and blue colours
Option 4)
separate the blue colour part from the red and green colours