Ray Optics and Optical Instruments - Result Question 37

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37. 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 $1.5 \times 10^{11} m$. What is the diameter of the Sun’s image on the paper?

======= ####37. 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 $1.5 \times 10^{11} m$. What is the diameter of the Sun’s image on the paper?

3e0f7ab6f6a50373c3f2dbda6ca2533482a77bed:content/english/neet-pyq-chapterwise/physics/ray-optics-and-optical-instruments/ray-optics-and-optical-instruments—result-question-37.md (a) $9.2 \times 10^{-4} m$

(b) $6.5 \times 10^{-4} m$

(c) $6.5 \times 10^{-5} m$

(d) $12.4 \times 10^{-4} m$

[2008]

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Answer:

Correct Answer: 37. (a)

Solution:

  1. (a) We have, $|\frac{v}{u}|=\frac{\text{ Size of image }}{\text{ Size of object }}$

or, Size of image $=|\frac{v}{u}|$, Size of object

$=(\frac{10^{-1}}{1.5 \times 10^{11}}) \times(1.39 \times 10^{9})$ $=0.92 \times 10^{-3} m=9.2 \times 10^{-4} m$

$\therefore$ Diameter of the sun’s image $=9.2 \times 10^{-4} m$.