Question

At what angle will a ray of light be incident on one face of an equilateral prism, so that the emergent ray may graze the second surface of the prism (n=2)?

Answer 1

Answer:

Hi MATE...

Maximum deviation occurs when there is grazing incidence.

Since, the prism is an equilateral one; its angles are 60o each.

Therefore, maximum deviation occurs when there is grazing incidence, that is, angle of incidence is 90o 

From Snell’s law μ= (sin i/sin r)

1.5= (sin90o)/ (sin r)

 r = sin-1 (0.67) = 420

Also, (r + r′) =A=60o

   r′= (60o−r)       

 = (60o−42o) =18o

Let the angle of emergence be i

 Then μ=1.5 = (sin i′/sin r′)

= sin i′=1.5sin18o

= (1.5×0.31) =0.465

∴    i′=sin−1 (0.465)=28o

hope it'll help you...