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 × 10^9 ~m and its mean distance from the earth is 1.5 × 10^ 11

Correct answer: B. 9.2 × 10^ -4 ~m Here, (D / 2)/(u)=(d / 2)/(f) aligned & =(D f)/(u) & = 1.39 × 10^8 × 10 × 10^ -2 1.5 × 10^ 11 =9.2 ×10^ -4 ~m aligned

NEET 2008

Exam: NEET
Year: 2008
Subject: Physics
Chapter: Ray Optics

NEET 2008 · Physics · Ray Optics

A boy is trying to start a fire by focusing Sunlight on a piece of...

A boy is trying to start a fire by focusing Sunlight on a piece of paper using an equiconvex lens of focal length

10 \mathrm{~cm}

. The diameter of the Sun is

1.39 \times 10^9 \mathrm{~m}

and its mean distance from the earth is

1.5 \times 10^{11} \mathrm{~m}

. What is the diameter of the Sun's image on the paper? A boy is trying to start a fire by focusing Sunlight on a piece of paper using an equiconvex lens of focal length 10

A boy is trying to start a fire by focusing Sunlight on a piece of paper using an equiconvex lens of focal length 10

Options

A $12.4 \times 10^{-4} \mathrm{~m}$
B $9.2 \times 10^{-4} \mathrm{~m}$
C $6.5 \times 10^{-4} \mathrm{~m}$
D $6.5 \times 10^{-5} \mathrm{~m}$

Correct answer

B. $9.2 \times 10^{-4} \mathrm{~m}$

Step-by-step solution

Here,

\frac{D / 2}{u}=\frac{d / 2}{f}

\begin{aligned} \Rightarrow \quadd & =\frac{D f}{u}\\ & =\frac{1.39 \times 10^8 \times 10 \times 10^{-2}}{1.5 \times 10^{11}}=9.2 \times10^{-4} \mathrm{~m} \end{aligned}

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