Question

The figure below shows path of ray of yellow light through a glass prism. The speed of yellow light in the prism is 1.88 x 10⁸m/s.

1. Determine the refractive index of the prism material for the light (speed of light in vacuum = 3.0 x 10⁸m/s (3mks)
2. Show on the diagram the critical angle C, and determine its value. 
3. Given that r=21.2°, determine angle Ө 
4. On the same diagram sketch the path of the light after striking the prism if the prism was replaced by another of similar shape but lower refractive index (use dotted line for your answer ) 

Answer 1

1. 3.0 x 10⁸m/s           (3mks)
   n = ^C/_V 
   = 3  x           10⁸
            1.88 x 10⁸ 
   = 1.596
   = 1.6 
2. 
   
   Sin C = ¹/_n 
            =    1   
               1.596 
         C = 38.8°
3. n = sin θ
         sin r
   1.596 =  sin θ   
               sin 21.2
   θ = 35.25