Question

22-3) an object, 5 cm tall is placed 60 cm in front of converging lens, f = 12cm. (a) find image distance, (b) compute the size of the image and wether it is erect or inverted.

Answer 1

Converging lens means convex lens

given data

height of the object = 5 cm

distance between object and lens =60 cm

focal length of the lens = 12 cm

a) Image distance

by lens formula

where

v=distance between image and lens

u = distance between object and lens

f = focal length

and

here

u = - 60 cm , f = 12 cm

putting values we get

Image distance is 15 cm

2) size of the image

we know

m is magnification , h_i is height of image _, h_o height of object

and also

hence

here v = 15 cm , u = -60 cm h_o= 5 cm

then

height of the image will be 1.25 cm (1/4 times of the object) ( negative sign indicates INVERTED image )