Question

an object 50 cm high is placed 1 m in front of a converging lens whose focal length is 1.5 m. determine the image height (in cm).

Answer 1

Given :

An object 50 cm high is placed 1 m in front of a converging lens whose focal length is 1.5 m.

To Find :

the image height (in cm).

Solution :

By lens formula :

$\dfrac{1}{v} - \dfrac{1}{u} = \dfrac{1}{f}$

Here, u = - 100 cm

f =  150 cm

$\dfrac{1}{v} - \dfrac{1}{-100} = \dfrac{1}{150}\\\\v = - 300 \ cm$

Now, magnification is given by :

$m = \dfrac{v}{u} = \dfrac{h_i}{h_o}\\\\h_i = \dfrac{300}{100}\times 1\\\\h_i = 3 \ m$

Therefore, the image height is 3 m or 300 cm.