A ray of light strikes a 45-45-90 prism as shown, reflects twice and reverses it

Question

A ray of light strikes a 45-45-90 prism as shown, reflects twice and reverses its direction. (i) Assuming the prism is in air, what is the lowest value of n possible for the prism? (ii) When this prism is placed in a liquid with an n-value of 1.27 there still are two reflections. When the prism is put into a liquid with an n-value of 1.46 then the reflection is not total. How does this limit the values of n for the prism? (iii) Is it possible for light to enter the prism as shown, and have only one (total) reflection?

Explanation / Answer

a)n1.sin1=n2.sin2:Snell's law

n2=1,2=90:limiting case for air

1=45

on solving n1=1.414

b)n2=1.27 2=90

1=45

on solving n1=1.79

c)It is not possible beacuse always the value of 1 will be 45deg so the equations will remain same

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