## College Physics (4th Edition)

(a) $E = 3.70\times 10^{-7}~eV$ (b) $8.45\times 10^{29}$ photons are emitted per second.
We can find the energy of each photon: $E = hf$ $E = (6.626\times 10^{-34}~J~s)(89.3\times 10^6~s^{-1})$ $E = (5.917\times 10^{-26}~J)(\frac{1~eV}{1.6\times 10^{-19}~J})$ $E = 3.70\times 10^{-7}~eV$ (b) We can find the number of photons per second that are emitted: $\frac{P~t}{E} = \frac{(50.0\times 10^3~W)(1~s)}{5.917\times 10^{-26}~J} = 8.45\times 10^{29}$ $8.45\times 10^{29}$ photons are emitted per second.