Answer
(a) The total energy of a single pulse is $1.20\times 10^{-12}~J$
(b) The intensity during a pulse is $2.39\times 10^5~W/m^2$
Work Step by Step
(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 $2.39\times 10^5~W/m^2$
