Posted by Anonymous on Thursday, June 6, 2013 at 12:25am.
Orange light with a wavelength of 6.00x102nm is directed at a metallic surface with a work function of 1.60eV. Calculate:
a) The maximum kinetic energy of the emitted electrons
b) Their maximum speed
c) The cutoff potential necessary to stop these electrons (V=Ek/e)

physics  herp_derp, Thursday, June 6, 2013 at 12:37am
wait...did u mean a wavelength of "6.00 x 10^2"?
if so...these are my answers
a) first convert the numbers
6.00 x 10^2 nm = 6 x 10^7 m
1.60 eV = 2.56 x 10^19
then, plug in the numbers in this equation:
KE = hc/l  w
KE = (6.63E34)(3E8)/(6E7)  (2.56E19) = 7.55E20 J
b) for the velocity, use the ususal kinetic energy equation and solve for velocity
KE = (1/2)mv^2
then...
v = squroot(2 x KE/m)
(assuming the mass is an electron...)
v = squroot(2 x (7.55E20)/(9.1094E31)) = 4.0714E5 m/s
c) i have no idea how to do...srry bout that mate...
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