(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A flashlight is shining into a box. There are no reflections. We know the power of the flashlight in Watts. We know the volume of the box.

Question: How much energy (associated with the EM field) is in the box?

2. Relevant equations

3. The attempt at a solution

Integrate the power density (J s^-1 m^-3) over the volume of the box. But what is the power density?

Hints would be preferred over full solutions :)

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Light in a Box

**Physics Forums | Science Articles, Homework Help, Discussion**