Multiple choice

A Converging lens of power 4 D is kept in contact with a diverging lens of power - 2 D. The nature and the focal length of the combination is-

  1. Converging 25 cm

  2. Converging 50 cm

  3. Diverging 25 cm

  4. Diverging 50 cm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The combined power is 4 D + (-2 D) = 2 D (positive, so converging). Focal length = 1/Power = 1/2 = 0.5 m = 50 cm. A positive power means converging lens. The diopter (D) unit is the reciprocal of focal length in meters.

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