Light from a luminious point on the lower face of a rectangular glass slab , 2 cm thick, strikes the upper face and the totally reflected rays outline a circle of 3.2 cm radius on the lower face. Find the refractive index of the glass.

Answer

`1.17`

Explanation

Let refrective index =`mu`

From snell's law `mu "sin"theta_(C) = 1. "sin"90^(@) = "sin"theta_(C) = (1)/(mu)`
`"tan"theta_(C)= (1)/(sqrt(mu^(2)-1)) = (3.2)/(2)`
`mu^(2) -1 ((10)/( 16))^(2) , mu = (sqrt(356))/(16) = 1.17`