Question

A ray of light travelling through rarer medium is incident at very small angle i on a glass slab and after refraction its velocity is reduced by 20%. The angle of deviation
A. `(i)/(8)`
B. `(i)/(5)`
C. `(i)/(2)`
D. `(4i)/(5)`

Answer 1

Correct Answer - B
`V_(m)=80%" of "V_(a)=0.8V_(a)`
`:.mu=(sini)/(sinr)=(V_(a))/(V_(m))=(V_(a))/(0.8V_(a))`
`:.(i)/(r)=1.25" "i.e.,i=1.25r`
Thus, `delta=i-r`
`=i-(i)/(1.25)=(1.25i-i)/(1.25)`
`=i((0.25)/(1.25))=(i)/(5)`