Question

(i) Define critical angle.
(ii) State one important factor which affects the critical angle of a given medium.

Answer 1

(i) The angle of incidence for which the angle of refraction is 90o is called critical angle. 

`"_1  mu _2 = (sin i_c)/(sin (90^circ))`

`therefore (mu_2)/(mu_1) = (sini_c)/(1)`

` therefore 1/mu = sini_c " If " mu_2 = 1  mu_1 = mu`

` therefore  i_c = sin^(-1) (1/mu)`

(ii) Relative refractive of the medium `("_1 mu_2)`1