#### Electromagnetic Waves Model Questions

12th Standard EM

Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 50
5 x 1 = 5
1. The dimension of $\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } }$ is

(a)

[LT-1]

(b)

[L2T-2]

(c)

[L-1T]

(d)

[L-2T2]

2. During the propagation of electromagnetic waves in a medium

(a)

electric energy density is double of the magnetic energy density

(b)

electric energy density is half of the magnetic energy density

(c)

electric energy density is equal to the magnetic energy density

(d)

both electric and magnetic energy densities are zero

3. The EM waves do not transport

(a)

energy

(b)

charge

(c)

momentum

(d)

information

4. Which EM waves are used in medicine to destroy cancer cells?

(a)

(b)

IR

(c)

૪ rays

(d)

UV rays

5. A magnetic field is produced by

(a)

a changing electric field

(b)

a moving charge

(c)

both of them

(d)

none of them

6. 6 x 2 = 12
7. What is meant by Fraunhofer lines?

8. Write the uses of Radio waves.

9. Write the uses of Micro waves.

10. Why are Infra~ed radiation referred as heat waves? Name the radiations, which are next to these radiation having
(i) shorter λ
(ii) longer λ.

11. Draw a diagram depicting oscillating electric and magnetic field of an electromagnetic wave.

12. What is the orgin of displacement currtent?

13. 6 x 3 = 18
14. Consider a parallel plate capacitor which is maintained at potential of 200 V. If the separation distance between the plates of the capacitor and area of the plates are 1 mm and 20 cm2. Calculate the displacement current for the time in μs.

15. Write down the properties of electromagnetic waves.

16. Discuss the source of electromagnetic wave.

17. What is emission spectra?. Give their types.

18. What is absorption spectra?. Give their types.

19. Write the frequency source of production and uses of Ultraviolet radiation.

20. 3 x 5 = 15
21. Let an electromagnetic wave propagate along the x direction, the magnetic field oscillates at a frequency of 1010 Hz and has an amplitude of 10−5 T, acting along the y - direction. Then, compute the wavelength of the wave. Also write down the expression for electric field in this case.

22. In a plane Electromagnetic wave the electric field oscillates sinusoidally at a frequency of 1.5 X 1010Hz & amplitude 36 Vm-1.
(i) What is the wavelength of a wave?
(ii) What the amplitude of the oscillating magnetic field?
(iii) Straight the average energy density of the electric field $\left( \overrightarrow { E } \right)$ , is equal to average energy density of the magnetic field $\left( \overrightarrow { B } \right)$

23. Use the formula E = h૪ (for energy of a quantum of radiation photon) and obtain the photon energy in units of ev for different parts of the Electromagnetic spectrum. In what ways are the different scales of photon energies that you obtain related to the sources of Electromagnetic radiation?