Question

A moth is at a distance of $10cm$ in front of a plane mirror. An observer is standing at a distance of $30cm$ in front of the mirror. Calculate the distance between the observer and the position of the moth's image.

• A. $30cm$
• B. $50cm$
• C. $10cm$
• D. $40cm$

Answer 1

The correct option is D $40cm$

For a plane mirror, the image distance $=$ the object distance from the mirror.
Given, the moth is $10cm$ in front of the mirror. So, the image of the moth is formed $10cm$ behind the mirror.

The observer is standing at a distance of $30cm$ in front of the mirror.
That is, the distance between the observer and the mirror is $30cm$.

Therefore, the distance between the moth's image and the observer is $30cm+10cm=40cm$.