Question

An object of height 10 cm is placed at a distance of 40 cm, infront of a concave mirror of focal length 20 cm Find

th length of image.

Answer 1

Answer

Object distance u=-40 cm

Focal length of concave mirror f=-20 cm

Using mirror formula

$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$

$=>v=\frac{uf}{u-f}\\=\frac{-40\times(-20)}{-40+20}\\=-40cm$

Distance of the image is -40 cm.

So height of image

$h_i=h_0{\frac{-v}{u}\\=\frac{10\times(-(-40)) }{10}}$ =-40cm