Question

Consider the situation shown in figure. Water $\left( \mu _ { w } = \frac { 4 } { 3 } \right)$ is filled in a beaker upto a height of 10 cm. A plane mirror is fixed at a height of 5 cm from the surface of water. Distance of image from the mirror after reflection from it of an object O at the bottom of the beaker is –

• A. 15 cm
• B. 12.5 cm
• C. 7.5 cm
• D. 10 cm

Answer 1

Answer: (B)

12.5 cm

Answer 2

Distance of first image (I₁) formed after refraction from the plane surface of water is $\frac { 10 } { 4 / 3 }$ = 7.5 cm

from water surface $\left( \mathrm { d } _ { \text {app } } = \frac { \mathrm { d } _ { \text {actual } } } { \mu } \right)$

Now distance of image is 5 + 7.5 = 12.5 cm from the plane mirror.