- #1

- 124

- 0

## Homework Statement

ok, well...im not sure if this is posted in the right section but ive just come across a past exam question that is supposed to be in classical mech and relativity section of the paper...

If 1.3kW/m

^{2}of solar radiation falls on the Earth at midday at the equator what is the total force from this solar radiation on the Earth? (you may assume that all the radiation is absorbed)

And so what is the rate of loss of mass from the sun due to solar radiation?

Earth radius [r] = 6400km

Sun-Earth distance [R] = 1.5x10

^{11}

[Assume circular orbit]

Earth mass [m] = 6x10

^{24}kg

Sun mass [M] = 2x10

^{30}kg

## The Attempt at a Solution

okay so i had no idea how to start at first by using classical mech methods, so i decided to try and use methods from my quantum course:

P = [stephans const]*T

^{4}

so T = 4th root[1300 / 5.67x10

^{-8}] = 389.1258K

[wavelength]*T = 2.8x10

^{-3}

so [wavelength] = 7.1956x10

^{-6}m

and so E = hc/[wavelength] = 2.764x10

^{-20}J

and Fd = change in E -> energy all gets absorbed so it is converted into other forms of E

so E after is zero

and so F = E/d = 1.84x10

^{-31}N

but i have no idea if this is right, or even if this method is valid...any help would be greatly appreciated...

Also i didnt know how to get started on the 2nd part of the qu

btw...after typing this up in this post i dont think this is right at all cause i think some of my units are a bit messed up...

Last edited: