Question

The focal length of a convex lens is 20 cm. If an object of height 2 cm is placed at 30 cm from the lens, find 

(i) the position and nature of the Image 

(ii) the height of the image 

(iii) the magnification produced by the lens.

Answer 1

Data: Convex lens, f = 20 cm,

u = -30 cm, h₁ = 2 cm, v = ?, h₂ = ?, M = ?

The image will be formed at 60 cm from the lens and on the other side of the lens with respect to the object. It is a real image.

h₂ is negative. This shows that the image is inverted. The height of the image -4 cm.

(iii) M = \(\frac{h_2}{h_1}=\frac{-4cm}{2cm}\) = -2

M is negative, indicating that the image is inverted.

The magnification produced by the lens = -2.