Everything You Need To Know About Electromagnetic Waves

Before we start our today’s topic let’s talk about the topic first. I mean-

What are E.M waves?

If there exists a variable electric field and magnetic field in any place, then it spreads around like a wave called Electromagnetic Wave.

Properties of E.M waves:

  1. E.M waves are formed by accelerated ionized particles.
  2. No medium is required for the propagation of E.M waves.
  3. The velocity of E.M waves = velocity of light
  4. In free space velocity of E.M waves ⇒C=1/√𝜇0𝝐0
  5. In any other medium velocity of E.M waves ⇒v=1/√𝜇𝝐
  6. E.M waves follow the principle of superposition.
  7. In free space relation between E and B is, c=E/B
  8. When E.M waves propagate they carry energy with them. This energy is equally divided into an electric field and a magnetic field.

Scientist Maxwell expresses the four basic laws of electricity and magnetism with the help of four equations. The laws are-

  1. Gauss law for static electricity
  2. Gauss law for magnetism
  3. Faraday’s law for electromagnetic induction and
  4. Maxwell-Ampere rotation law

Now the equations are-

  1. âˆĢE.ds=q/𝝐0 {E & ds are vector quantity}. It is independent of time and equally applicable for static and dynamic charges. From this equation, it comes to know that the electric force line is not a closed curve.
  2. âˆĢB.ds=0 {B & ds are vector quantity}.It is also independent of time. From this equation, it comes to know that the existence of a single magnetic pole is not possible and the magnetic force line is a closed curve.
  3. âˆĢE.dl= -d/dt(âˆĢB.ds) . It depends on time. According to this equation, the path integration of the electric field in a closed path is equal to the change in electric flux in that path.
  4. âˆĢB.dl=𝜇0{I+đœē0(d𝜑E/dt)} .{đœē0(d𝜑E/dt)=iD(displacement current)} It is also depend on time. From this equation, we can conclude that changing the electric fields can produce a magnetic field.

Now it’s time to some important points,

  1. If light propagating in x-direction it can be written as E=E0(𝜔t-x/c) &B=B0(𝜔t-x/c) { B0 =amplitude of magnetic field, E0 = amplitude of electric field, 𝜔 = angular frequency}
  2. Radiation pressure: It is exerted upon any surface due to the exchange of momentum between the object and the electromagnetic field. Radiation pressure, p=(2I/c)r+ (I/c)(1-r) {r=reflection coefficient}
    p=I/c ; for complete absorption
    p=2I/c ; for complete reflection
  3. The energy density of electromagnetic field: u= 𝝐0E2/2 + B2/2𝜇0
  4. Average energy density = 𝝐0E2/2 = B2/2𝜇0

These are the basic things you have to know in this chapter.

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Snehasish Konger
Snehasish Konger

Hey, I'm Snehasish Konger, the guy behind this website.
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