Navigate

When an object is placed 40cm from a diverging lens, its virtual image is formed 20 cm

When an object is placed 40cm from a diverging lens, its virtual image is formed 20 cm from the lens. The focal length and power of lens are

Options

(a) F=-20 cm, P=-5 D
(b) F=-40 cm, P=-5 D
(c) F=-40 cm, P=-2.5 D
(d) F=-20 cm, P=-2.5 D

Correct Answer:

F=-40 cm, P=-2.5 D

Explanation:

We have, 1 / f = (1/v) – (1/u) ⇒ 1 / f = (1/-20) – (-1/40) = (-1 + 1) / 40 = 1 / 40

f = – 40 cm

Power of the lens, P = – (200 / 0.40) = – 2.5 D

JK2013
admin:

Related Questions

  1. An inclined plane of length 5.60m making an angle of 45⁰ with the horizontal is placed
  2. The rest energy of an electron is
  3. The ratio of longest wavelength corresponding to Lyman and Blamer series
  4. The energy released in the fission of 1 kg of ₉₂U²³⁵ is (energy per fission = 200 MeV)
  5. A plane wave of wavelength 6250Å is incident normally on a slit of width 2×10⁻² cm.