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A convex lens of focal length 40 cm forms an image of an extended source of light on a photoelectric cell. A current I is produced. The lens is replaced by another convex lens having the same diameter but focal length 20 cm . The photoelectric current now is

Options

  1. AI 2
  2. B4 I
  3. C2 I
  4. DI

Correct answer

D. I

Step-by-step solution

For a light of any given frequency, the photoelectric current is directly proportional to the intensity of light. As the diameter of the lens remains the same, both lenses will collect the same amount of light. Therefore, the intensity of the light will remain the same. Hence, this is the correct option.

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