# Is there an equation for the energy loss of a photon in different media?

1. Jan 25, 2012

### Ralphonsicus

Thanks.

2. Jan 25, 2012

### Staff: Mentor

If a photon is absorbed, it loses 100% of its energy. If it doesn't get absorbed, it loses 0% of its energy.

What you can talk about is the probability of absorption for a single photon, which translates into the (average) fraction of a large number of photons that gets absorbed when passing through something.

Typically you have an exponential absorption law, in which the number of surviving photons decreases with thickness of the absorbing material according to an "absorption coefficient" which depends on photon energy and the type of absorber:

$$N = N_0 e^{-\alpha \Delta x}$$