Question

A thin convex lens forms a virtual image when an object is placed on the principal axis at a distance of 12 cm from the lens. When the object is moved away from the lens along the principal axis through a distance of 18 cm, the lens forms a real image. If the magnification of the virtual image is five times the magnification of the real image, then the focal length of the lens is

• A. 27 cm
• B. 18 cm
• C. 15 cm
• D. 12 cm

Hint:

For a convex lens: \[ m=\frac{v}{u} \] and \[ \frac{1}{f}=\frac{1}{v}-\frac{1}{u} \] Many lens problems can be solved directly by combining these two relations.

Answer 1

The Correct Option is B