Question

(i)A divergent lens has a focal length of 20cm.At what distance should an object of height 4cm from the optical centre of the lens be place so that its image is formed 10cm away from the lens.
(ii)Draw a ray diagram to show the formation of the image in above situation.

Answer 1

Answer:

u = -20cm

height of image = 2cm

Explanation:

given

f=-20cm

v=-10cm

height of object=4cm

formula:-

1/f = 1/v - 1/u

1/u = 1/v - 1/f

1/u = -1/10 + 1/20

1/u = -2+1/20

1/u = -1/20

u = -20

magnification =v/u=hi/ho

-10/-20=hi/4

1/2=hi/4

hi=2cm