- #1
alanf
- 15
- 0
On my E&M final, a question asked 1) how much energy a light beam transferred to a non-reflective object in x seconds (3 joules), 2) what pressure the light exerted on the object during that time, and 3) what energy would be transferred to a perfectly reflective mirror by the same beam of light. The answer to 3 was zero, which seems intuitive - 100% of the energy has to be returned into space - yet the pressure on the mirror should be twice that on the absorptive object. So it should gain momentum. So how can it gain no energy?