Question

Q11. A convex lens has focal length of 20 cm. Calculate at what distance from the lens should
the object be placed so that the image is formed at 40 cm on the other side of the lens? Also
state the nature of the image formed.
[3]​

Answer 1

Answer:

u= -40cm

Explanation:

f =20 cm

v =40 cm

u=?

Using lens formula

¹/f =¹/v -¹/u

¹/u =¹/v -¹/f

¹/u =¹/40-¹/20

¹/u= 1-2/40

¹/u= -1/40

u = -40

Object should be placed at 40cm from the lens to form a image 40 cm on the other side of the lens

m= v/u

m= 40/-40

m= -1

If magnification is -1

It means that image formed is real and inverted and of the same size as the object