Question

distance between an object and a screen is 80cm a convex lens is placed between the object and the screen the maximum focal length of the lens for which and image will be formed on the screen isThe distance between an object and a screen is 80cm.A convex lens is placed between the object and the screen the maximum focal length of the lens for which and image will be formed on the screen
a)10cm
b)15cm
c)20cm
d)25cm


Please explain it ...... what's the correct answer and why​

Answer 1

Dear Puja,

◆ Answer - (c) 20cm

f <= 20 cm

◆ Explanation -

For formation of a real image by convex lens, minimum distance distance between object & screen must be four times the focal lens.

D >= 4f

f <= D/4

f <= 80/4

f <= 20 cm

Therefore, maximum focal length of the lens for which and image will be formed on the screen is 20 cm.

Hope u understand. Thanks for the question..