Question

An object is placed 20 cm infront of a block of glass 10 cm thick having its farther side silvered. The image is formed 23.2 cm behind the silvered face. The reflective index of glass is

• A. 1.41
• B. 1.46
• C. 1.51
• D. 1.61

Answer 1

Answer: (C)

1.51

Answer 2

AB' = Apparent depth = x, AB = 10 cm

AB' = x = $\frac { \mathrm { AB } } { \mu }$= $\frac { 10 \mathrm {~cm} } { \mu }$ ...(i)

M point shift to M'

by reflection law

OM' = M'I

20 +x = (10 – x) + 23.2

20 + $\frac { 10 } { \mu }$= 33.2 – $\frac { 10 } { \mu }$, $\frac { 20 } { \mu }$= 13.2

µ = $\frac { 200 } { 132 }$= $\frac { 50 } { 33 }$ = 1.51