## College Physics (4th Edition)

(a) The total energy of a single pulse is $1.20\times 10^{-12}~J$ (b) The intensity during a pulse is $2.39\times 10^5~W/m^2$
(a) We can find the energy of a single pulse: $E = P~t$ $E = (120.0\times 10^{-3}~W)(10.0\times 10^{-12}~s)$ $E = 1.20\times 10^{-12}~J$ The total energy of a single pulse is $1.20\times 10^{-12}~J$ (b) We can find the intensity during a pulse: $I = \frac{P}{A}$ $I = \frac{P}{\pi~r^2}$ $I = \frac{120.0\times 10^{-3}~W}{(\pi)(0.40\times 10^{-3}~m)^2}$ $I = 2.39\times 10^5~W/m^2$ The intensity during a pulse is $2.39\times 10^5~W/m^2$