Question

A rectangular slab of refractive index μ is placed over another slab of refractive index 3, both slabs being identical in dimensions. If a coin is placed below the lower slab, for what value of μwill the coin appear to be placed at the interface between the slabs when viewed from the top

• A. 1.8
• B. 2
• C. 1.5
• D. 2.5

Answer 1

Answer: (C)

1.5

Answer 2

Apparent depth of coin as seen from top $= \frac { x } { \mu _ { 1 } } + \frac { x } { \mu _ { 2 } } = x$

$\Rightarrow \frac { 1 } { \mu _ { 1 } } + \frac { 1 } { \mu _ { 2 } } = 1$ $\Rightarrow \frac { 1 } { 3 } + \frac { 1 } { \mu } = 1$

$\Rightarrow \mu = 1.5$