Electromagnetic Waves: Important part-A 2 marks Short Questions and Answers

ANNA UNIVERSITY PART 'A' QUESTIONS AND ANSWERS

1. Write any five properties of electromagnetic waves.

The Five Properties of electromagnetic waves are as follows

(i) Electromagnetic waves are transverse in nature.

(ii) No medium is required for propagation of electromagnetic waves.

(iii) Electromagnetic waves travels with the speed of light i.e, 3×10⁸ ms^‒1 (vacuum).

(iv) It is not deflected by electric or magnetic field.

(v) It exhibits interference / diffraction.

2. Write the expression for electromagnetic wave equations in terms of electric and magnetic field vector for free space.

(i). Wave equation in terms of electric field 

(ii). Wave equation in terms of magnetic field 

ADDITIONAL PART 'A' QUESTIONS & ANSWERS

1. Define electric intensity

Electric intensity is defined as the ratio of electrostatic Force (field exerts by charge) to electric charge.

2. What is mean by electric displacement vector?

It is defined as electric flux per unit area. It is also known as Electric flux density.

3. Define electrical permittivity.

Electrical permittivity is defined as the ratio of displacement current to electric field.

Electrical permittivity ε= ε₀ε_r

4. Define dielectric constant (or) Relative permittivity.

Dielectric constant (or) Relative permittivity is defined the ratio of permittivity of the medium to permittivity of free space or vacuum.

Relative permittivity ε_r = ε/ε₀

ε = ε₀ε_r

5. Define magnetic flux density.

Magnetic flux density is defined as the number of magnetic lines of force passing normally through unit area of cross section at that point.

6. Define magnetic field intensity.

Magnetic field intensity is defined as the force experienced by a unit north pole placed at the given point in a magnetic field.

7. Define magnetic permeability.

Magnetic permeability is defined as ratio of magnetic flux density to magnetic field intensity.

Magnetic permeability μ = μ₀μ_r  = 

It is the measure of degrees at which the lines of force can penetrate through the material.

8. Define relative permeability

Relative permeability is defined as the ratio of permeability of the medium to permeability of free space or vacuum.

Relative permeability μ_r = μ/μ₀

(or) μ= μ₀μ_r

9. State the Gauss's law.

Gauss law states that, the total flux through any closed surface is equal 1/ε₀ times the total charge enclosed in the surface.

10. State the Faraday's law of electromagnetic induction.

It states that, the induced electro motive force in a coil is equal to the rate of change of the magnetic flux linking the coil.

 ε = ‒ dϕ/dt

Where, ε is the electro motive force and Ō is the magnetic flux.

11. State the Ampere's circuit law.

Ampere's circuit law state that, the line integral of magnetic field surrounding any closed path is equal to μ₀ times of net current passing through that path.

12. What you mean by equation of continuity.

Law of conservation of charge states that the total charge of an isolated system remains constant. The differential form of mathematical representation of law of conservation of charge is called equation of continuity.

 (∇.J + ∂ρ/∂t ) = 0

13. What is meant by displacement current?

The rate of change of charge in a capacitor is said to be a displacement current.

 I_D = ∂Q/∂t [where Q is Charge]

14. State the Gauss divergence theorems

It states that, "the volume integral of divergence of a vector  is equal to the vector  that spreads out through the surface which covers the volume (V).

15. State the Stoke's theorems

It states that, "the line integral of a vector  around a closed contour (line) is equal to the surface integral of curl over the region which is bounded by the contour."

16. Write down the Maxwell's equations in differential form.

Maxwell's equations in differential form

17. Write down the Maxwell's equation in integral form

Maxwell's equation in integral form

18. Write down the Maxwell's Equations for free space in differential form.

Maxwell's equations for a free space or vacuum in differential form are as follow

19. What is mean by plane electromagnetic wave?

If the field vector of electromagnetic wave is constant over any plane that is perpendicular to the directon of wave propagation at any instant of time, then this wave is called plane electromagnetic wave.

20. Write any two properties of plane electromagnetic waves in free space.

1. EM wave travel with the speed of light in vacuum.

2. EM wave field vectors  and  are perpendicular to each other and they are also perpendicular to the direction of wave propagation.

3. Field vectors  and  are in same phase.

21. List out any four sources of electromagnetic waves.

Source: Electromagnetic waves

1. Accelerating charges: Radio waves

2. Fast collisions of electrons: X‒rays

3. Nuclear decay: Gamma rays

4. Hot object, Human body and sun: Infra‒Red rays

22. Write short notes on cell phone reception.

Cell phone is a two‒way communicating radio, consisting of a radio wave transmitter and a radio wave receiver.

Cell phones contain radio antenna to receive radio signals and it is a metallic element (such as copper) engineered to be an effective size and shape for transmitting and receiving definite frequencies of radio waves.

Receiver antenna converts the radio wave to an electric signal, this receiving and converting function is said to be cell phone reception.

23. Why electromagnetic wave is of transverse in nature.

Electric field vector and magnetic field vectors are mutually perpendicular to each other and also perpendicular to the wave propagation direction. These three are mutually perpendicular to each other. Therefore electromagnetic wave is said to be transverse in nature.