Optics Question 991

Question: A point source of light is placed 4 m below the surface of water of refractive index 5 / 3. The minimum diameter of a disc which should be placed over the source on the surface of water to cut?off all light coming out of water is

[CBSE PMT 1994; JIPMER 2001, 02]

Options:

A) 2 m

B) 6 m

C) 4 m

D) 3 m

Show Answer

Answer:

Correct Answer: B

Solution:

Here $ \sin i=\frac{1}{\mu }=\frac{3}{5} $ .

and hence $ \tan i=\frac{3}{4}=\frac{r}{4} $ .

This gives $ r=3m $ , hence diameter = $ 6m $



NCERT Chapter Video Solution

Dual Pane