from some Lithium atomic spectrum which is equal 0.162A.This corresponds to 0.36cm-1
I still struggling to get this answer ,because if i take reciprocal of of it i can not get 0,36cm-1
It would be a good start to figure out what are the quantities you are dealing with.
What quantity is given in A? Is it a wavelength?
And then what quantity do you want to calculate? Is it inverse wavelength or maybe the magnitude of the wave vector?