What should be the value of angle  so that light entering normally through the surface AC of a prism (n = 3/2) does not cross the second refracting surface AB.

Explanation

Light ray will pass the surface AC without bending since it is incident normally. Suppose it strikes the surface AB at an angle of incidence i.

`i=90^(@)-theta`
For the required condition :
`90^(@)-theta gt C`
or `sin (90^(@)-theta) gt sin C`
or `cos theta gt sin C`
`=1/(3//2)=2/3`
or `theta lt "cos"^(-1) 2/3`