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
A. infinite
B. 6 cm
C. 4 cm
D. 3 cm
Answer:B
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
A. infinite B. 6 cm C. 4 cm D. 3 cm