Question

A biconvex lens of focal length 15 cm is in front of a plane mirror. The distance between the lens and the mirror is 10 cm. A small object is kept at a distance of 30 cm from the lens. The final image is

• A. Virtual and at a distance of 16 cm from the mirror
• B. Virtual and at a distance of 20 cm from the mirror
• C. Real and at a distance of 16 cm from the mirror
• D. Real and at a distance of 20 cm from the mirror

Answer 1

The correct option is C Real and at a distance of 16 cm from the mirror


Object is placed at O.
First refraction through lens
$\frac{1}{v}\frac{1}{30}=\frac{1}{+15}$
$\Rightarrow v=+30cm$
$\Rightarrow$ Real image is formed at A.
This image acts as virtual object for plane mirror. Image is formed 20 cm before mirror (B) This acts as virtual object for lens.
Second refraction through lens
$\frac{1}{v}\frac{1}{+10}=\frac{1}{+15}$
$\Rightarrow v=+6:$ Real image
Distance from mirror is 16 cm.