Question
Physics Question on Ray optics and optical instruments
A disc is placed on a surface of pond which has refractive index 5/3.A source of light is placed 4 m below the surface of liquid. The minimum radius of disc will be so light is not coming out
A
∞
B
3m
C
6m
D
4m
Answer
3m
Explanation
Solution
The correct option is(B): 3m sin θc =1/µ =1/(5/3)⇒r/√4^2+r^2 ⇒r=3m