Question
A ray of light, incident on a equilateral glass prism moves parallel to the base of the prism inside it. What is the angle of incidence for this way?
Solution
Given, an equilateral glass prism.
Angle of prism = 60o
Refractive inex of the medium, =
When light ray moves parallel to the base of the prism inside it, then
r1 = r2
so that ,the minimum deviation takes place.
For minimum deviation r = A/2 =
Now, using Snell's law,
is the required angle of incidence so that, the ray travels parallel to the base ofthe prism.