Question

A convex mirror of focal length 10 cm is shown in figure. A linear object AB = 5 cm is placed along the optical axis. Point B is at distance 25 cm from the pole of mirror. What will be the size of image of AB

Answer 1

For Point A

$f=10cm$

Object distance $AB=5cm$

$u=-25cm$

Now,

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

$\frac{1}{v}=-\frac{1}{-25}+\frac{1}{10}$

$v=\frac{50}{7}cm$

For point B

$f=10cm$

$u=-30cm$

Now,

$\frac{1}{v}=-\frac{1}{-30}+\frac{1}{10}$

$v=\frac{30}{4}cm$

Size of image AB $=\frac{30}{4}-\frac{50}{7}=0.36cm$