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en/13.4.12.md
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| + | ### Statement | ||
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| + | $13.4.12.$ [Insert the problem statement] | ||
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| + | ### Solution | ||
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| + | While folding a planoconvex lens along its diameter reduces its light-collecting area by a half, the new (half) biconvex lens has half the focal length and produces the image of the the Sun (which is very far) with half the diameter as well. Thus a half of the energy is concentrated on a quarter of the image area, and the intensity of the image of the Sun will double. | ||
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| + | #### Answer | ||
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| + | [Insert a concise answer or boxed result] | ||
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| ### Statement | |||
| $13.4.12.$ [Insert the problem statement] | |||
| ### Solution | |||
| While folding a planoconvex lens along its diameter reduces its light-collecting area by a half, the new (half) biconvex lens has half the focal length and produces the image of the the Sun (which is very far) with half the diameter as well. Thus a half of the energy is concentrated on a quarter of the image area, and the intensity of the image of the Sun will double. | |||
| #### Answer | |||
| [Insert a concise answer or boxed result] | |||