JEE Main & Advanced Physics Ray Optics Sample Paper Topic Test - Refraction of Light Through Curved Surfaces

  • question_answer
    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 \[1.39\times {{10}^{9}}\,m\] and its mean distance from the earth is \[1.5\times {{10}^{11}}\text{ }m\]. What is the diameter of the sun's image on the paper?

    A) \[9.2\times {{10}^{-4}}m\]

    B) \[6.5\times {{10}^{-4}}m\]

    C) \[6.5\times {{10}^{-5}}m\]

    D) \[12.4\times {{10}^{-4}}m\]

    Correct Answer: A

    Solution :

    [a] From the relation \[\frac{I}{O}=\frac{v}{u}\] Here,     \[O=1.39\times {{10}^{9}},\]   \[v=0.1\,m,\] \[u=1.5\times {{10}^{11}}m\] \[\therefore \]      \[l=\frac{0.1}{1.5\times {{11}^{11}}}\times 1.39\times {{10}^{9}}\]\[=9.2\times {{10}^{-4}}m\]

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