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^{-28}k

^{2}Joules

k = 5.8 x 10

^{9}m

^{-1}

Find the group velocity.

i know that the equation for v

_{g}= 2pi/h (dE/dk)

dE/dk = 2(2.5 x 10

^{-28}) = 5.0 x 10

^{-28}k

plugging in k, i get

dE/dk = 2.9 x 10

^{-18}J/m

v

_{g}= 2.75 x 10

^{16}m

^{-1}s

^{-1}

what i am more concerned about here is the fact that my units should be m/s (or at least i think so), not 1/m-s. can anyone tell me why i'm getting the wrong units?