The critical angle is maximum when light travels from

Options

A. water to air
B. air to water
C. glass to air
D. glass to water

Answer

D

Explanation

For critical angle (c) , the ray must travel from a denser medium to a rarer medium . So it is not possible in the case of air to water (b).
(i) When it travels from glass to air,
`""_(a) n_(w) = (1)/(sin c_(1)) = (4)/(3) therefore sin c_(1) = (3)/(4) = 0.75`
(ii) When it travels from glass to air
`""_(a) n_(g) = (1)/ (sin c_(2)) = (3)/(2) therefore sin c_(2) = (2)/(3) = 0.67`
(iii) When it travels from glass to water , `""_(w) n_(g) = (1)/(sin c_(3))`
`therefore (""_(a) n_(g))/(""_(a) n_(w)) = (3//2)/(4//3) = (9)/(8) = (1) / (sin c)`
`therefore sin c_(3) = (8)/(9) = 0.9`
Thus sin c and hence c is maximum , when it travels from glass to water .