A concave mirror with its optic axis vertical and mirror facinig upward is placed at the bottom of the water tank. The radius of curvature of the mirror is 40 cm and refractive index for water `mu=4//3` . The tank is 20 cm deep and if a bird is flying over the tank at a height of 60 cm above the surface of water, find the position of image of the bird.

Explanation

`(4//3)/(v)+(1)/(60)=(((4)/(3)-1))/(oo)=0`
`v=-80 cm`
`I^(')` acts as an object for the mirror.
`:. (1)/(v)+(1)/(-100)=(-1)/(20)`
`rArr v=-25cm`
`I^('')` will serve as an object for the plane surface.
`:. (1)/(v)-((4//3))/(5)=((1-(4)/(3)))/(oo)`
or `v=+3.75cm`