Question

The size of the image of an object, which is at infinity, as formed by a convex lens of focal length 30 cm is 2 cm . If a concave lens of focal length 20 cm is placed between the convex lens and the image at a distance of 26 cm from the convex lens, calculate the new size of the image.

(a)  1.25 cm

(b)  2.5 cm

(c)  1.05 cm

(d)  2 cm . 

Answer 1

Correct option  (b) 2.5cm 

Explanation:

Convex lens forms the image at  l₂ and is at the second focus of convex lens. Size of  l₁  = 2 cm .  l₁ acts as virtual object for concave lens. Concave lens forms the image