Answer
See the answer below.
Work Step by Step
$c=\lambda\times\nu$
$\nu=2.998\times10^8\ m/s\div 470 \times10^{-9}\ m=6.38\times10^{14}\ 1/s$
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:
$2.5\times10^{-14}\ J/4.23\times10^{-19}\ J/photon=$
$59,102\ photons$
