< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Okay, I am having trouble with the units. I have the values for the wavenumber and I am trying to find the period. These are the formulas that I am trying. T = 1/f ; f = c/lambda example: lambda = 3657 cm^-1 ; c = 2.998 x 10^8 m/s I am doing 2.998 x 10^8 m/s / (3657 cm^1 x (1 cm/0.01m)) however, the unit for frequency is Hz = 1/s I am getting m^2 on the denominator. Am I using the right formulas? thanks!