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Geometrical Optics question

2008 · Q137
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Geometrical Optics question

2008 · Q137

NEETPhysicsGeometrical OpticsMCQ+4 / −1
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 ×\times× 109 m and its mean distance from the earth is 1.5 ×\times× 1011 m. What is the diameter of the sun's image on the paper ?
  1. A
    6.5 ×\times×10−-−5 m
  2. B
    12.4 ×\times×10−-−4 m
  3. C
    9.2 ×\times×10−-−4 m
  4. D
    6.5 ×\times×10−-−4 m
View written solutionFree

Correct answer: C

∣vu∣=\left| {{v \over u}} \right| = ​uv​​=

size of image
size of object



Size of image = $$\left| {{v \over u}} \right|$$ $ \times $ Size of object

= $$\left( {{{{{10}^{ - 1}}} \over {1.5 \times {{10}^{11}}}}} \right) \times \left( {1.39 \times {{10}^9}} \right)$$

= 9.2 ×10–4 m

$ \therefore $ Diameter of the sun’s image = 9.2 ×10–4 m
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