# Homework Help: Heisenberg Uncertainty Maximum Lifetime of Photon

1. Mar 21, 2013

### diggleM

1. The problem statement, all variables and given/known data
In special conditions, it is possible to measure the energy of a gamma ray photon to 1 part in 10^15. For a photon energy of 50 keV, estimate the maximum lifetime that could be determined be a direct measurement of the spread of photon energy.

2. Relevant equations
ΔtΔE≥$\hbar$/2

3. The attempt at a solution

It seems simple enough using the given equation to solve for the maximum lifetime, however I'm not sure I'm understanding how the relative uncertainty of 1 part in 10^15 effects the problem. If someone would be able to explain how the relative uncertainty effects the calculation to me, it would be much appreciated.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Mar 21, 2013

### Simon Bridge

Take another look at Heisenbergs relation - what do each of the terms mean?

3. Mar 21, 2013

### diggleM

The way I understand it, they can be thought of as terms of uncertainty for time and energy, which are inversely related. That is to say, if you measure the Energy to a high level of certainty, the level of uncertainty will be high as well.

Looking back in my text describing the relation, it mentions that if a particle has a definite energy, ΔE = 0. This leads me to thinking that to solve a value for ΔE, you could find the relative uncertainty where Relative Uncertainty = | uncertainty/measured quantity|, in this case the relative uncertainty would be 10^15 and measured quantity would be 50,000 eV, to solve for the uncertainty, ΔE, which could be used to solve for Δt.

These are still pretty new concepts to me so I'm not sure if that is an appropriate mode of thinking about this. Does that seems to makes sense or do you see flaws in my thought process?

4. Mar 21, 2013

### Simon Bridge

If you know a measurement x to 1 part in 1000 then the relative uncertainty would be about 1/1000 and the uncertainty would be Δx=x/1000.

Use a value of planks constant in units of keV.(time) to avoid conversions.