The block shown above is made of glass of refractive index for green light 1.3 a

Question

The block shown above is made of glass of refractive index for green light 1.3 and is surrounded by air. Green laser light Inside the block is totally reflected if the angle smaller than a is can never totally reflect less than 50.3 degree less than 100.6 degree greater than 100.6 degree greater than 50.3 degree If the blue laser light is used in the same set-up, the angle of total internal reflection a_blue is larger than a the same as a smaller than a undefined because green laser doesn't totally reflect

Explanation / Answer

Given

   refractive index of glass is n1 = 1.3 , green light entering from glass to air of refractive index is n2 = 1

from Snell law n1 sin alpha 1 = n2 sin alpha2

   here sin alpha2 = 90

       1.3 sin alpha1 = 1 sin 90

           sin alpah1 = 1/1.3
           alpha1 = arc sin (1/1.3)
           alpha1 = 50.285 degrees

           alpha1 = 53 degrees

as we know that the refractive index is n = c/V

and v = lambda*f

   where the frequency is same in all the media but the wavelength is different and changes

we know that the wavelength of green light is larger than the blue light (laser)

   so the angle of incident is less than alpha1

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