Question

An object of height 3 cm is placed at 10 cm from a concave lens of focal length 15 cm. Find the size of the image.

Answer 1

Object distance u = 10 cm 

Focal length of a concave lens f= -15 cm 

Let v be the image distance,

Distance of image v = 6 cm 

Magnification m =\(\frac{v}{u}\) =\(\frac{6}{10}\) = 0.6 

And Magnification m =\(\frac{h'}{h}\) 

Where h’ – height of image 

h – height of object

0.6 = \(\frac{h'}{3}\)

∴ h’ = 3 × 0.6 = 1.8 cm 

∴ Height of image = 1.8 cm