A ray of light passes through an equilateral glass prism such that the angle of incidence is equal to the angle of emergence and each of these angles is equal to 3/4 of angle of prism. Find the angle of deviation.
OR
Calculate the speed of light in a medium whose critical angle is 45°. Does critical angle for a given pair of media depend on the wavelength of incident light? Give reason.Given, i = e = ¾ A, …(1)
where,
A is the angle of prism.
Angle of deviation for a ray of light in a prism is given by,
Prism is an equilateral triangle.
That is A= 60o
OR
Using the snell's law we have
... (1)
where, C is the critical angle of the medium and 
is the refractive index of the medium.
Also, 
... (2)
Now, from equations (1) and (2), we have 
This is the speed of the light in the medium.
Refractive index of a medium is inversely proportional to the wavelength of light. So, critical angle also depends upon the wavelength of incident light.
