Question

Q29. Critical angle is that angle of incidence in denser
medium for which angle of refraction in rarer
medium is :
(A) 900
(B) 800
(C) 600
(D) 400​

Answer 1

Answer:    r+r′+990∘=180∘

∴r′=90∘−r

Futher,i=r

Applying Snell's law μDsini=μR sin r'

or μDsinr=μRsin(90∘−r)=μRcosr

∴muRmuD=tanr,θC=sin−1(μRμD)=sin−1(tanr)

∴ Correct option is (a).