Question

An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm

. (a) Draw a ray diagram for the formation of image.

(b) Calculate the image distance.

(c) State two characteristics of the image formed.

Answer 1

the mirror formula is given as

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

here

f = focal length = -20cm

v = image distance

object distance ,$u\text{= -10cm}$

so, $\frac{1}{-20}=\frac{1}{v}+\frac{1}{-10}$

$\frac{1}{v}=\frac{1}{-20}+\frac{1}{10}$

$\frac{1}{v}=\frac{-1+2}{20}=\frac{1}{20}$

$v=20cm$

The ray diagram below

a

so, the image formed is erect, magnified and virtual.