Question

what happens if you hold the paper at a distance shorter than the focal length from the concave mirror and move it away

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Answer 1

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The ray from sun after reflection from the mirror , shall converge at focus. Holding a sheet of paper at the focus,may cause it to burn if she reflected rays are very strong but if a sheet of paper is held very close to the mirror , it will lie between the pole and the focus and hence shall only warm up.

Answer 2

Answer:

First we can find a blurred image and as we move away, we find a brighter spot on the paper. The point where we get a brighter spot is the focus.