Here, uD/2=fd/2 ⇒d=uDf=1.5×10111.39×108×10×10−2=9.2×10−4 m
A boy is trying to start a fire by focusing Sunlight on a piece of paper using an equiconvex lens of focal length 10 cm. The diameter of the Sun is 1.39×109 m and its mean distance from the earth is 1.5×1011 m. What is the diameter of the Sun's image on the paper?
Held on 30 Apr 2008 · Verified 9 Jul 2026.
12.4×10−4 m
9.2×10−4 m
6.5×10−4 m
6.5×10−5 m
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