Question

what will be the value of critical angle when light enters from a denser medium into a lighter medium and the velocity of light is twice in the lighter medium than in the denser medium
(A) 45°
(B) 30°
(C) 60°
(D) 15°​

Answer 1

HEY:-)

LET speed of the Light in the Rarer medium be ' a ' m/s.

Since , Speed of light in denser medium =  2 × speed of light in rarer medium.

=2a m/s.

Now,

 ₁μ₂= speed  of  the  light  in  first  medium / speed  of  light  in second medium 

= 2a/a 

μ = 2

We know that ,

sini /sinr = 1/μ

as r=90 , i=c .then

sin c = 1/μ

c= sin⁻ (1/μ) 

c= sin⁻(1/2)

c= 30°

Hence the critical angle is 30°

HopE U gOT

Answer 2

Answer:

(B) 30°

Explanation:

refractive index is inversely proportional to velocity of light,u of medium is 1/2. so

sin(theta)=usin(90°) since when critical angle is formed angle if refraction is 90° so theta =sininverse(1/2)

theta=30°