Question

Since intensity increases the number of photons that pass through a point in a second, why is intensity regarded differently as frequency when the two seem to be the same? According to my chem book intensity is independent of frequency.

Answer 1

Yes, the intensity depends, in part, on the frequency.

Intensity is power per unit area. Power is energy per time. For a photon, the energy is hν. So, the intensity will be

I=Nhν/A

if N is the monochromatic photon emission rate (photons per second), ν is the frequency of the photons, and A is the area these photons are hitting.

If the only thing one changes is the frequency of the photons, then doubling the frequency will double the intensity. Alternately, doubling only the emission rate, or focusing the photons to hit half the area will also double the intensity.

In the explanation you saw, maybe n is the photons per time per area so that n=N/A

I hope you got it