Chapter 38 - Quantization - Exercises and Problems - Page 1115: 39

$P = 4.32\times 10^{-10}~W$

We can find the energy of each photon: $E = \frac{h~c}{\lambda}$ $E = \frac{(6.626\times 10^{-34}~J~s)(3.0\times 10^8~m/s)}{460\times 10^{-9}~m}$ $E = 4.32\times 10^{-19}~J$ We can find the power of the flash: $P = \frac{N~E}{t}$ $P = \frac{(10^8)(4.32\times 10^{-19}~J)}{0.10~s}$ $P = 4.32\times 10^{-10}~W$