Question

A ray of light falls normally on a face of a glass slab. What are the values of values of angle i and angle r.
B) Light enters from air to diamond which has refractive index of 2.52.
Calculate the speed of light in diamond

Answer 1

A) Both i, r are equal to zero, i=r=0. B) $\frac{v_{1}}{v_{2}} = n_{21}$. Speed of light in diamond = speed in vacuum/refractive index. V=1.19×$10^{8}$.

Answer 2

A)
       when the ray falls normally on a surface, angle of incidence is 0. 
   since μ₁ Sin i = μ₂ sin r    =>  r is also zero.  The ray goes straight in to the glass medium and emerges out of glass slab at the other surface also at  i = 0 and r = 0. 

B)
           Refractive Index is defined as the ratio of speed of light in vacuum divided by speed of light in the medium.  It is also calculated by the formula: Sin i / Sin r.

             μ = 2.52 = 3 * 10⁸ m /sec / v

               v = 3 * 10⁸ / 2.52 = 1.19 * 10⁸ meters / sec