Instead of studying for my Networks II final tomorrow, I'm procrastinating by studying electromagnetic radiation instead. One thing I'm curious about is this: How does an increase in the energy of em radiation affect its intensity? I'm having a hard time tracking down a good solid definition of intensity. Most places just describe it in terms of more photons or waves, but what units are those?

I would think that for a given intensity in terms of total output from a source, that much fewer photons would be needed as the energy of the radiation increased. For example, 1W of radiation from a point source in the radio spectrum would require a whole lot more photons than it would in the UV spectrum. The thing is, I don't know if 'photons' is even the correct term, or what the relationship is between them.

Intensity is the energy flux at a point: from a source radiating in all directions, the intensity diminishes by an inverse square with respect to distance. Wavelength/frequency does not affect this relationship. Power does, and because of the conservation of energy the intensities at all points on a sphere centered on the radiation source is equal to the power.

Photons are light energy quanta. Waves are waves. They aren't really units.

The term you're looking for here is power, but assuming you're developing some software concerned with light properties it might make more sense to accept a light power in terms of intensity at some constant distance.

I'm just curious, it's not for any project.

Instead of taking the energy flux through some radial measure, or area, I'm simplifying it by considering the total power output from a point source.

My source of confusion lies in the make up of the light for any given power output. To achieve 1W of power for example, will fewer photons be required for higher frequency radiation vs. lower frequency radiation? What is the relationship there?