## Chemistry and Chemical Reactivity (9th Edition)

$c=\lambda\times\nu$ $\nu=2.998\times10^8\ m/s\div 470 \times10^{-9}\ m=6.38\times10^{14}\ 1/s$ Per photon: $E=h\times\nu$ $E=6.626\times10^{-34}\ J.s\times 7.31\times10^{14}\ 1/s=4.23\times10^{-19}\ J$ Number of photons: $2.5\times10^{-14}\ J/4.23\times10^{-19}\ J/photon=$ $59,102\ photons$