Question

A wooden stick of length $100cm$ is floating in water while remaining vertical. The relative density of the wood is 0.7. The apparent length of the stick when viewed from top [close to the vertical line along the stick] is $xcm$. Find $x/10$. Refractive index of water $=\frac{4}{3}$ (Write upto two digits after the decimal point.)

Answer 1

Since relative density of wood is $0.7$, so 30% length of the stick will lie outside water.
The lower end will be at a distance of $70cm$ from the surface of the water.
Apparent depth of the lower end is,
$h=\frac{70}{\left(\frac{4}{3}\right)}cm=52.5cm$
Apparent length of stick = $30cm+52.5cm=82.5cm$