Chapter 4, Problem 16P

The power output of a laser is measured by its wattage, that is, the number of joules of energy it radiates per second $\left(\text{1 W}={\text{1 J s}}^{-\text{1}}\right)$ . A 10-W laser produces a beam of green light with a wavelength of 520 nm $\left(\text{5}.\text{2}\times \text{1}{0}^{-\text{7}}\text{m}\right)$ .

(a) Calculate the energy carried by each photon.

(b) Calculate the number of photons emitted by the laser per second.