Q.

Two transparent media A and B are separated by a plane boundary. The speed of light in those media are 1.5×108m/s and 2.0×108m/s respectively. The critical angle for a ray of light for these two media is                [2022]
 

1 sin-1(0.500)  
2 sin-1(0.750)  
3 tan-1(0.500)  
4 tan-1(0.750)  

Ans.

(2)

For medium A, speed of light vA=1.5×108m/s

For medium B, speed of light vB=2.0×108m/s

For medium A, nA=cvA=3×1081.5×108=2

For medium B, nB=cvB=3×1082×108=1.5

The critical angle for a ray of light is,

sinC=nBnA  ;  C=sin-1(1.52)  ;  C=sin-1(0.750)