A boy is trying to start a fire by focusing sunlight on a piece of paper using an equiconvex lens of focal length `10cm`. The diameter of the sun is `1.39xx10^(9)m` and its mean distance from the earth is `1.5xx10^(11)m`. What is the diameter of the sun's image on the paper ?

Options

A. `9.2xx10^(-4)m`
B. `3.5 xx10^(-4)m`
C. `1.2 xx 10^(-3)m`
D. `12.4 xx 10^(-5)m`

Answer

C

Explanation

The light is focused on a paper.
`therefore v=f=10cm=10^(-1)m`
and the distance of the object = distance of the sun from the lens
`therefore u=1.5 xx 10^(11) m`
The diameter of the sun `= o =1.8 xx 10^(9) m`
and I is be found out by using, `(I)/(o) =(v)/(u)`
`therefore (I)/(1.8xx10^(9))=(10^(-1))/(1.5xx10^(11))`
`therefore I=(1.8xx10^(8))/(1.5xx10^(11))=1.2xx10^(-3)m`
`therefore` The diameter of the sun's image `=1.2 xx 10^(-3) m`