So, it is basically a wave form both in time T as well as in distance X. In fact, by
definition 2 pi by lambda is called K. This is known as a, this is by definition, one calls it
as a wave number, this is by definition. You define 2 pi by lambda equal to K. In other
words, instead of writing 2 pi by lambda, you write it as K. What is K? K is actually
inverse of the wave length, in a sense 2 pi by lambda, 2 pi is a constant. So, this is an
inverse of a wave length. So, this wave number is essentially an inverse of a wave length.
In other words, it may be a measure of how many wave lengths are there in a given
length. And 2 pi by T is of course, very common is called omega, that is wave frequency.
This of course everybody knows that, wave frequency is the inverse of 2 pi by T.