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 × 109 m and its mean distance from the earth is 1.5 × 1011 m. What is the diameter of the sun's image on the paper?

Question

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 × 109 m and its mean distance from the earth is 1.5 × 1011 m. What is the diameter of the sun's image on the paper? (A)  6.5 x 10 5m  (B) 12.4 × 10-4 m  (C)  9.2 x 10 4m  (D)  6.5 x 10 4m

Tardigrade Admin · Accepted Answer

(size of image/size of object ) = | (v/u)| ⇒ size of the image = ( 1.39 × 109 × 10-1/ 1.5 × 1011) = 0.92 × 10-3 m = 0.92 × 10 -3 m size of the image = 9.2 × -4 m

Q. 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?

$6.5 x 1 0^{5} m$

$12.4 \times 1 0^{- 4} m$

$9.2 x 1 0^{4} m$

$6.5 x 1 0^{4} m$

$\frac{s i zeo f ima g e}{s i zeo f o bj ec t} = ∣ \frac{v}{u} ∣$
$\Rightarrow s i zeo f t h e ima g e = \frac{1.39 \times 10 ^{9} \times 10 ^{- 1}}{1.5 \times 10 ^{11}} = 0.92 \times 10^{- 3} m$
$= 0.92 \times 10^{- 3} m$
size of the image $= 9.2 \times^{- 4} m$

Q. 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 1.39×109 m and its mean distance from the earth is 1.5×1011m. What is the diameter of the sun's image on the paper?

6.5x105m

12.4×10−4m

9.2x104m

6.5x104m