Answer
$4.6\times 10^{26}~photons~~$ are emitted.
Work Step by Step
We can find the total energy emitted in the form of photons during the bulb's lifetime:
$E = (60~W)(0.93)(730~h)(3600~s/h) = 1.466424\times 10^8~J$
We can find the photon energy:
$E = \frac{hc}{\lambda}$
$E = \frac{(6.63\times 10^{-34}~J\cdot s)(3.0\times 10^8~m/s)}{630\times 10^{-9}~m}$
$E = 3.157\times 10^{-19}~J$
We can find the total number $N$ of photons emitted:
$N = \frac{1.466424\times 10^8~J}{3.157\times 10^{-19}~J/photon} = 4.6\times 10^{26}~photons$
$4.6\times 10^{26}~photons~~$ are emitted.
