Question

The power of a lens in +5 diopters.What is the nature and focal length of this lens? At what distance from this lens should an object be placed so as to get its inverted image of the same size?PLZ ANSWER IN A CORRECT MANNER​

Answer 1

the lens is a convex lens since power is '+' 5.

focal length (f) = 1/power.

the power of lens is reciprocal of focal length taken in metre.

so, 1/5 = 0.2 m

which is equal to 20 cm.

Inverted image of same size will be obtained when object is placed at 2F,

which is double of focal length.

so, 20*2 = 40 cm.

object must be placed 40cm from lens to obtain an inverted image of same size.