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. The electric field at a distance 3R / 2 from the centre of a charged conducting
  2. A U²³⁵ reactor generates power at a rate of P producing 2×10⁸ fission per second.
  3. Two charges of equal magnitude q are placed in air at a distance 2a
  4. A meter stick of mass 400 g is pivoted at one end and displaced through an angle 60°.
  5. A shell of mass 200 g is ejected from a gun of mass 4 kg by an explosion