Question

A concave lens is used to produce a magnification of +1/4. If the focal length of the lens is 24 cm then the distance between the object and image will be
a) 18 cm
b) 54 cm
c) 72 cm
d) none of the above

Answer 1

Answer:

option A

Explanation:

given magnification M=1/4

focal length =24cm

since M=v/u

therefore

u=4v

since

1/f=1/v-1/u (lens formula)

1/24=1/v-1/4v

1/24=(4v-v)4v²

1/24=3v/4v²

1/24=3/4v

v/24=3/4

v=3×24/4=3×6=18cm