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?
(Refractive index of water =$\frac{4}{3}$)

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

Answer 1

The correct option is C 12 cm

Let it be filled to height 'h'cm. Then the part not in water is (21-h)cm.
So the apparent depth of the filled portion must be (21-h)cm.
$\frac{realdepth}{apparentdepth}=refractiveindexofwater$
$\frac{h}{21-h}=1.33$
$h=12cm$
hence, 12cm water should be filled in a container.