Question

A coin is kept at bottom of an empty beaker. A traveling microscope is focussed on the coin from the top, now water is poured into beaker up to a height of $10cm$. By what distance and in which direction should the microscope be moved to bring the coin again in focus

• A. 10 cm upward
• B. 10 cm downward
• C. 2.5 cm upwards
• D. 2.5 cm downwards

Answer 1

The correct option is C

2.5 cm upwards

When water is poured in the beaker. Coin appears to shift by a distance $d=\frac{h}{4}=\frac{10}{4}=2.5cm$
Hence to bring the coil again in focus, the microscope should be moved by $2.5cm$ in the upward direction.