A vessel contains water up to a height of 20 cm and above it an oil up to another 20 cm. The refractive indices of the water and the oil are 1.33 and F30 respectively. Find the apparent depth of the vessel when viewed from above.

Explanation

Shift due to water
`Dt_w=1-(1/mu)d`
`=[-(1/1.33)]20`
`=1/4(20)=5cm`
Shifted to oil,
`Dt_0=[1-(1/1.33)]20`
`=4.6 cm`
`Total shift `Kt=5+4.6=9.6cm`
Apparent depth =40-(9.6)`
`=30.4 cm`
between the surface.