A layer of benzene (μ = 1.6) of thickness 6 cm floats on water (μ′ = 1.33) of depth 4 cm in a vessel. When viewed vertically through air, find the apparent distance of the bottom of the vessel below the surface of benzene (to the nearest cm)
Physics · Mixed Chapter
JEE Mains

Question

A layer of benzene (μ = 1.6) of thickness 6 cm floats on water (μ′ = 1.33) of depth 4 cm in a vessel. When viewed vertically through air, find the apparent distance of the bottom of the vessel below the surface of benzene (to the nearest cm)

Physics · Mixed Chapter

G1 Physics · Accepted Answer

Step 1: At near-normal incidence, apparent thickness of a layer viewed from air is actual thickness divided by refractive index. Step 2: Benzene apparent thickness = 6/1.6=3.75 cm. Water apparent thickness =4/1.33≈3.01 cm. Step 3: Total apparent depth =3.75+3.01=6.76 cm. Nearest centimetre =7 cm. Answer: 7.