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. 12 cm
• C. 14 cm
• D. 10.5 cm

Answer 1

Answer: (B)

Let it be filled to height h.then the part not in water is $(21-h)$

So, the real depth of container $=h$,and apparent depth of water $=21-h$.

Refractive index $=\frac{Realdepth}{Apparentdepth}$

$\frac{h}{21-h}=\frac{4}{3}$

$3h=4\times 21-4h$

$3h+4h=4\times 21$

$7h=4\times 21$

$h=12cm$

Hence, option C is correct.