The focal length of a convex lens is 25 cm. At what distance from the optical centre of the lens an object be placed to obtain a virtual image of twice the size ?

Open in App

Solution

focal length ,f=+25 cm
image is virtual and magnified ,m=+2

For a lens ,magnification is;
m=v/u
+2=v/u
v=2u
Lens formula is
1/f=1/v-1/u
1/25=1/2u-1/u
-1/2u=1/25
u=-12.5 cm

Suggest Corrections

Similar questions

0.15 m

10

The distance at which an object should be placed from a thin convex lens of focal length 10 cm to obtain a virtual image of double of its size is

Where should an object be placed in front of a convex lens to get a real image of the size of the object?

(a) At the principal focus of the lens

(b) At twice the focal length

(d) Between the optical centre of the lens and its principal focus.

Join BYJU'S Learning Program