Question

How much water should be filled in a container, $21$ cm in height, so that it appears half-filled when viewed from the top of the container?

• A. $8cm$
• B. $10.5cm$
• C. $12cm$
• D. $14cm$

Answer 1

The correct option is C $12cm$

Let height upto which water should be filled be $h$

For container to appear half filled,

Height of Empty part = Apparent height of filled part

Refractive index of water = 4/3

$\to (21-h)=\frac{h}{\frac{4}{3}}$

$h$ = 12 cm