Question 389: Ray Optics

Question

A biconvex lens has a radius of curvature of magnitude 20 cm. Which one of the following options describe best the image formed of an object of height 2 cm placed 30 cm from the lens ?

Accepted Answer

Focal length of the lens
$${1 \over f} = \left( {1.5 - 1} ight)\left( {{1 \over {20}} - {1 \over { - 20}}} ight)$$
$$ \Rightarrow $$ f = 20 cm
From lens formula
$${1 \over v} - {1 \over u} = {1 \over f}$$
$$ \Rightarrow $$ $${1 \over v} - {1 \over { - 30}} = {1 \over {20}}$$
$$ \Rightarrow $$ v = 60 cm
$${I \over O} = m = {v \over u}$$ = $${{60} \over { - 30}}$$ = -2
$$ 	herefore $$ I = -2 $$ 	imes $$ (O) = -2 $$ 	imes $$ 2 = -4 cm
So image will be real inverted and of size 4 cm.

Answer

Virtual, upright, height = 1 cm

Answer

Virtual, upright, height = 0.5 cm

Answer

Real, inverted, height = 4 cm

Answer

Real, inverted, height = 1 cm

Ray Optics

A biconvex lens has a radius of curvature of magnitude 20 cm. Which one of the following options describe best the image formed of an object of height 2 cm placed 30 cm from the lens ?

Choose the correct answer: