Question 395: Ray Optics

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

Accepted Answer

$$\left| {{v \over u}} ight| = $$
size of image
size of object
Size of image = $$\left| {{v \over u}} ight|$$ $$ 	imes $$ Size of object
= $$\left( {{{{{10}^{ - 1}}} \over {1.5 	imes {{10}^{11}}}}} ight) 	imes \left( {1.39 	imes {{10}^9}} ight)$$
=  9.2 ÃÂ10
Ã¢ÂÂ4
m
$$ 	herefore $$ Diameter of the sunÃ¢ÂÂs image = 9.2 ÃÂ10
Ã¢ÂÂ4
m

Answer

6.5 $$ 	imes $$10$$-$$5 m

Answer

12.4 $$ 	imes $$10$$-$$4 m

Answer

9.2 $$ 	imes $$10$$-$$4 m

Answer

6.5 $$ 	imes $$10$$-$$4 m

Ray Optics

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

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