Question

Two identical thin converging lenses brought in contact so that their axes coincides are placed `12.5cm` form an object. What is the optical power of the system and each lens, if the real image formed by the system of lenses if four times as large as the object?

Answer 1

Correct Answer - `10D`, Optical pwer of each lens `= 5D`
`u = -12.5cm, m = (v)/(u) = -4, rArr v = +50`
Alsor, `(1)/(f) = (1)/(v) - (1)/(u) rArr = (1)/(f) = (1)/(+50) - (1)/-12.5) = (+1+4.)/(50) = (1)/(10)`
`f = 10cm = (1)/(10)m`
`P = (1)/(f) = 10D`
Power of each lens `= (P)/(2) = 5D`