Whenever a visible light with electric field E= t strikes the Oxygen or Nitrogen atom, the electron revolving around the nucleus gets accelarated with an accelaration a. There will be two forces acting on an electron orbiting the nucleus. Firstly, there is an external force =qE(Basic definition) . When this force acts on an electron, the electron starts to accelarate. At that time, there will be a restoring force =-K where K=(Constant defined by an atom).
Mathematically K can be defined as =
Applying Newton’s second law of motion to the accelarating charge(Oxygen or Nitrogen atom).
= + =ma where m=mass of an electron and a=accelaration.
Divide both L.H.S and R.H.S by m.
= – + t