So, this is basically a sine curve. So in other words, I will write in next slide that if you
have here a curve xi equal to xi a cos K X minus omega T, this represents a wave form
with frequency omega, where K equal to 2 pi by lambda and omega equal to 2 pi by T, T
equal to wave period. This is by definition. Whenever you find a curve, whenever you
want to plot something cos K X minus omega T, it always means that it is a wave of
wave length K and frequency omega, that is all. You take a computer program and try to
plot that for a given T for a given X a number of points, you will see that they will all look like that.