# Energy from the sun

## Homework Statement

Energy from the sun (distance 1.496 x 10^11m from earth) arrives at the earth at a rate of 1400W/m^2. How fast is the sun losing mass due to energy radiation?

## The Attempt at a Solution

Ok so i thought that Ei = E/r^2 where Ei is incident radiation and E is radiation at source..

Therefore E sun = r^2 (1400)

Then using E=mc^2..I divide the result by c^2 to give mass loss per second..

but i don't get the right answer..where am i going wrong?
thanks

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Filip Larsen
Gold Member
The solar constant specifies how much power sun light contains per square meter at our distance from the sun. To get the total power output of the sun light you would then need to know "how many" square meters there are all around the sun at our distance from it.

Doc Al
Mentor
You are given the power per unit area at a certain distance from the sun. What's the total area over which the sun's energy is spread at that distance? (You're almost there.)