# How much energy would enter your pupils from an explosion in space?

cestlavie
Homework Statement:
Earth is about 28,000 light years from the center of the Milky Way Galaxy. If a supernova explosion occurred approximately 14,000 light years away from us and released ##2.0 * 10^46 J## of energy in a sudden burst of light, how much energy would enter one of your pupils? Assume the diameter of a pupil to be about 4 mm.
3.0 E 23 J
1.1 J
4.6 J
3.5 J
2.2 J
Relevant Equations:
##S_{average}= \frac {energy} {time} * \frac {1} {area}##
The answer is 1.1 J, but I don't know how to get there. The only equation I can think of that might be related to this is Intensity, which I've added above. I could find area, using .0004m as the diameter, and energy using 2.0 E 46 J, but I get stuck on energy.

Homework Helper
Gold Member
You need another relation. How does the intensity S of the light depend on the power of the source and the distance from the source?

• Delta2
Homework Helper
Gold Member
Also, check your conversion of 4 mm to meters.

• Delta2