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Wave Optics

Question
CBSEENPH12038295

A ray of light, incident on a equilateral glass prism (μmedium =3) 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, μ =3 

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  = 30° 

Now, using Snell's law,
                        μ = sin isin r

                 3  = sin isin 30° = sin i1/2 

                sin i = 32
                    i =sin-132 = 60° 
is the required angle of incidence so that, the ray travels parallel to the base ofthe prism.

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