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A boy is trying to start a fire by focusing Sunlight on a piece of paper using an equiconvex lens of focal length . The diameter of the Sun is and its mean distance from the earth is . What is the diameter of the Sun's image on the paper?

  1. A
  2. B
  3. C
  4. D

Solution & Step-by-step Explanation

The angular size of the Sun is the same as the angular size of its image formed at the focus (since Sunlight is coming from infinity).

Where = Diameter of Sun, = Distance of Sun, = Diameter of image, = focal length.


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A boy is trying to start a fire by focusing Sunlight on a piece of paper using an equiconvex lens of focal length . The diameter of the Sun is and its mean distance from the earth is . What is the diameter of the Sun's image on the paper?
A
B
C
D

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