Question

An object is placed at a distance of 4.5 cm to the left of a convex lens A of focal

length 4 cm.

(a) Find the distance from lens A where a screen should be placed to obtain the image.

(b) The screen is removed and the image is used as an object for a diverging lens B of

focal length 2 cm so that a real image is formed at a distance of 8 cm from lens B.

Find the distance between lens A and lens B.

Answer 1

a)

$f=\frac{dF_A}{d-F_A}=36~cm,$

b)

$f'=\frac{d'F_B}{d'+F_B}=1.6~cm,$

$l=f-f'=34.4~cm.$