Problem Fourteen. A green laser pointer has a power output of $1\mathrm{.}00$ mW and a wavelength of $530$ nm$.($THIS IS AN EXAM QUESTION.$)22.$ Find how many photons per second the laser emits in units of $1015$ photons$/$sec$.($A$)1\mathrm{.}29($B$)5\mathrm{.}38($C$)3\mathrm{.}86($D$)4\mathrm{.}38($E$)2\mathrm{.}67$ Problem Fifteen. Electrons are ejected from a metallic surface with speeds ranging up to $2\mathrm{.}50$ x $108$ m$/$s when light with a wavelength of m $121050.1$ is used. $($THIS IS AN EXAM QUESTION.$)23.$ Find the cutoff frequency for this surface in units of $1019$ Hz$.($A$)1\mathrm{.}33($B$)2\mathrm{.}67($C$)9\mathrm{.}95($D$)4\mathrm{.}38($E$)5\mathrm{.}38$ Problem Sixteen. X$-$rays having an energy of $850$ keV undergo Compton scattering from a target. The scattered rays are detected at $52\mathrm{.}0$ relative to the incident rays. $($THIS IS AN EXAM QUESTION.$)24.$ Find the kinetic energy of the recoiling electron $($in keV$).($A$)101($B$)331($C$)286($D$)538($E$)43225.$ Find the de Broglie wavelength of the recoiling electron in units of picometers. $($A$)5\mathrm{.}28$