# Wavelength vs Intensity

1. Dec 8, 2008

### Drax

hey everyone,

1. The problem statement, all variables and given/known data

I'm doing a sodium and mercury visible light spectroscopy lab at the moment. By using a PMT, I can detect the intensity of photons emitted as a function of wavelength (controlled parameter). I was wondering if anyone knows how the two relate theoretically.

The index of refraction I'm working with is that of air.

2. Relevant equations

n=sqrt(eps*mu) of air
U=1/2 eps E^2
U is the energy volume density stored by the Efield wave of the light
and E is not the Efield but somehow related to the amplitude.
P=Uv
I=P/A
E=hv?
possibly more?

3. The attempt at a solution

Well, I don't know too much yet about the wave equations describing electromagnetic radiation, but I do know how the de broglie wavelength relates to energy. The first equation I don't really understand in terms of derivation. Furthermore, I'm not sure if U relates to the complex or real amplitude squared of the E field. I'm very comfortable with the de broglie wavelength implications for photons but I'm not sure finding the Schrodinger energy of the photon will get me any closer to finding the power because of the uncertainty equation for energy and time. I'm lost at this point at how to approach relating Intensity to wavelength

Thanks for the help

2. Dec 9, 2008

### Drax

Nevermind. I figured it out.

For those who ever come across this,
hc/lamda = energy of photon,
but (hc/lamda)*N/T=Power
where N is the photon count and T is the time you count them for.
since A of the spectroscopy detector is far away from the source relative to its magnitude,
the curvature of the sphere of photons emitted is approximately parallel to A. Thus IA=P without worry of a cos term.