Measuring energy of photon to within some accuracy

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
Sign up Log in
2 replies · 2K views
quasar_4
Messages
273
Reaction score
0

Homework Statement



Estimate the minimum length of time needed to measure the energy of a photon to an accuracy of 10^(-15) Joules.

Homework Equations



E = hv, where v is the frequency of the photon and h is Planck's constant in J*s

Watts = Joules/second

The Attempt at a Solution



I can think of two ways to get the units to work out right, but I'm fairly certain they're not right. One would be to ignore the specific frequency of the photon, assuming that E is proportional to Planck's constant in J*s, and dividing to obtain an answer in seconds. But that seems unreasonable to me since the wavelength of the photon should plausibly matter.

The only other thing that comes to mind straight away is to somehow utilize the definition of watts, to determine how long it would take to get some wattage, but I don't feel that this is right, either.

What am I missing? I'm sure this is a simple, 30 second problem, I'm just having a mind block... :rolleyes:
 
Physics news on Phys.org

Discussion

Are you certain you need to use E = hv?
I think this is a problem dealing with the Heisenberg uncertainty princple, relating energy with time and Planck's constant. Maybe you should read up on it?
 
aha, that's perfect! I can't believe I didn't even think of it. I knew I was missing something easy. It's easy to derive the uncertainty principle with commutators, too, in case one has forgotten that as well. Thanks!

(See what 4 months of break from school does to the mind?? )