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 × 1 0 9 m and its mean distance from the earth is 1.5 × 1 0 11 m . What is the diameter of the Sun's image on the paper?

Here, u D /2 = f d /2 ⇒ d = u D f = 1.5 × 1 0 11 1.39 × 1 0 8 × 10 × 1 0 − 2 = 9.2 × 1 0 − 4 m

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Physics - Geometrical Optics Question with Solution | TestHub

PhysicsGeometrical OpticsRefraction at curved surface/LensHard2 minPYQ_2008

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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 $1.39 \times 1 0^{9} m$ and its mean distance from the earth is $1.5 \times 1 0^{11} m$ . What is the diameter of the Sun's image on the paper?

Options:

Answer:

Solution:

Here, $\frac{D /2}{u} = \frac{d /2}{f}$ $\Rightarrow d = \frac{D f}{u} = \frac{1.39 \times 1 0 ^{8} \times 10 \times 1 0 ^{- 2}}{1.5 \times 1 0 ^{11}} = 9.2 \times 1 0^{- 4} m$

Stream:NEETSubject:PhysicsTopic:Geometrical OpticsSubtopic:Refraction at curved surface/Lens

⏱ 2mℹ️ Source: PYQ_2008

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