Question

A concave lens has focal length of 15 cm. At what distance should the object from the lens be placed so that it forms an image at 10 cm from the lens? Also, find the magnification produced by the lens.

Answer 1

f = 15

V =-10

(As image of a real object can be formed on left side only Lens formula)

∴ Object should be kept at 30 cm from concave lens. 

m = v/u = -10/-30 = 1/3

∴ Magnification is 1/3 i.e. image is virtual, erect and smaller in size than object.