Consider three identical black barrels filled with water, as shown in the diagram at right. Each barrel has a different laser beam incident on it, as represented by the EM waves in the figure. The amplitude of the wave hitting barrel 2 is double that of barrel 1 (A=2A), but the wavelength is the same. The amplitude of the wave hitting barrel 3 is the same as that hitting barrel 1, but the wavelength is half (รยป/2).
a[3 points] Rank the barrels according to the rate at which they heat up. If any barrels heat up at the same rate, state so explicitly. Explain your reasoning.
b[7 points] Is the number of photons hitting barrel 2 each second (N) greater than, less than, or equal to the number of photons hitting barrel 3 each second (N)? First, explain your reasoning qualitatively, then determine a specific quantitative relationship and explain your reasoning.