## Physics (10th Edition)

Recall the equation E= hν, where E is the energy, h is Planck's constant and ν is the frequency. Energy of one FM photon =h$(91.9×10^{6}s^{-1})$ Energy of one AM photon= h($665×10^{3}s^{-1}$) Number of AM photons needed= Energy of one FM photon÷ Energy of one AM photon = $\frac{h(91.9×10^{6}s^{-1})}{h(665×10^{3}s^{-1})}$ = $\frac{91.9×10^{6}}{665×10^{3}}\approx138.2$ Since the number of protons cannot be a fraction, we need 139 photons.