CBSE Class 12 Physics Electro Magnetic Waves chapter notes and important questions

CBSE Class 12 Physics Electro Magnetic Waves chapter notes and important questions. There are many more useful educational material which the students can download in pdf format and use them for studies. Study material like concept maps, important and sure shot question banks, quick to learn flash cards, flow charts, mind maps, teacher notes, important formulas, past examinations question bank, important concepts taught by teachers. Students can download these useful educational material free and use them to get better marks in examinations.  Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

ELECTRO MAGNETIC WAVES

GIST

1. Conduction current and displacement current together have the property of continuity.

2. Conduction current & displacement current are precisely the same.

3. Conduction current arises due to flow of electrons in the conductor. Displacement current arises due to electric flux changing with time.

6. Electromagnetic Wave :- The wave in which there are sinusoidal variation of electric and magnetic field at right angles to each others as well as right angles to the direction of

wave propagation.

7. Velocity of EM waves in free space: 

8. The Scientists associated with the study of EM waves are Hertz, Jagdish Chandra Bose & Marconi.

9. EM wave is a transverse wave because of which it undergoes polarization effect.

10. Electric vectors are only responsible for optical effects of EM waves.

11. The amplitude of electric & magnetic fields are related by E/B=C

12. Oscillating or accelerating charged particle produces EM waves.

13. Orderly arrangement of electro magnetic radiation according to its frequency or wavelength is electromagnetic spectrum.

14. Hint to memorise the electromagnetic spectrum in decreasing order of its frequency. G X U V I M R

1. Write the SI unit of displacement current? 

Ans : Ampere

2. If B, B represent electric and magnetic field vectors of the electromagnetic waves, then what is the direction of propagation of the electromagnetic wave? 

Ans : 

3. Can the velocity of light in vacuum be changed?

Ans: Not possible

4. Calculate the wavelength of e.m waves emitted by the oscillator antenna system, if L=0.253 μH & C = 25Pf ?

Ans : 

5. The magnetic component of polarized wave of light is

B_X=(4×10^-6T) Sin [(1.57×10⁷m^-1)y+(4.5×10¹¹t)]

(a) Find the direction of propagation of light

(b) Find the frequency

(c) and wavelength write the expressions for electric field.

Ans :

6. Which physical quantity is same for X-rays of wavelength 10-10 m, red light of wavelength 6800 Å and radio wave of wavelength 500 m?  Ans:  Velocity

7. The amplitude B of harmonic electromagnetic wave in vacuum is Bo=510 n T. What is the amplitude of the electric field part of the wave? 

Ans : 153 N/C

8. Suppose E₀ =120 N/C and its frequency n = 50Hz. Find B₀ , ω,k and and write 0 0 expression for E and B ? 

Ans : 

9. The charging current for a capacitor is 0.25 A. what is the displacement current across its plates? 

Ans : 0.25 A

10. A variable frequency a.c source is connected to a capacitor. Will the displacement current increase or decrease with increasing frequency? 

Ans : Increases

11. e.m wave travel in a medium at a speed of 2x108 m/s. the relative permeability of the medium is 1.0. Calculate the relative ermittivity?

Ans : 

12. How does a charge q oscillating at certain frequency produce electromagnetic wave? 

Ans : Oscillating charge produces oscillating E which produces oscillating B and so on

13. How would you establish an instantaneous displacement current of 1A in the space between the parallel plates of 1μF capacitor? 

Ans : By changing the voltage dv/dt =10⁶ V/sec

14. Name the Maxwell’s equation among the four which shows that the magnetic monopole does not exist? 

Ans : Gauss’s theorem of Magnetism

15. Write the unit of µ₀ε₀ ?

Ans (m/s)^-2

16. Give reason for decrease or increase in velocity of light, when it moves from air to glass or glass to air respectively? 

Ans : The velocity of light depends on ε & μ of the medium.

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