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#### Electromagnetic waves Model Question Paper

12th Standard EM

Reg.No. :
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Physics

Time : 02:00:00 Hrs
Total Marks : 60
10 x 1 = 10
1. The dimension of $\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } }$ is

(a)

[LT-1]

(b)

[L2T-2]

(c)

[L-1T]

(d)

[L-2T2]

2. Which of the following are false for electromagnetic waves

(a)

transverse

(b)

mechanical waves

(c)

longitudinal

(d)

produced by accelerating charges

3. Th e electric and the magnetic field, associated with an electromagnetic wave, propagating along X axis can be represented by

(a)

$\vec { E } ={ E }_{ 0 }\hat { j }$ and $\vec { B } ={ B }_{ 0 }\hat { k }$

(b)

$\vec { E } ={ E }_{ 0 }\hat { k }$ and $\vec { B } ={ B }_{ 0 }\hat { j }$

(c)

$\vec { E } ={ E }_{ 0 }\hat { i }$ and $\vec { B } ={ B }_{ 0 }\hat { j }$

(d)

$\vec { E } ={ E }_{ 0 }\hat { j }$ and $\vec { B } ={ B }_{ 0 }\hat { i }$

4. In an electromagnetic wave in free space the rms value of the electric fi eld is 3 V m−1. The peak value of the magnetic field is

(a)

1.414 × 10-8 T

(b)

1.0 × 10-8 T

(c)

2.828 × 10-8 T

(d)

2.0 × 10-8 T

5. Which of the following is an electromagnetic wave?

(a)

α - rays

(b)

β - rays

(c)

$\gamma$ - rays

(d)

all of them

6. Let E = Eo sin[106 x -ωt] be the electric field of plane electromagnetic wave, the value of ω is

(a)

(b)

(c)

(d)

7. The electric and magnetic fields of an electromagnetic wave are

(a)

in phase and perpendicular to each other

(b)

out of phase and not perpendicular to each other

(c)

in phase and not perpendicular to each other

(d)

out of phase and perpendicular to each other

8. Electromagnetic waves are produced by

(a)

static charge

(b)

moving charge

(c)

an accelerating charge

(d)

chargeless particles

9. The EM waves do not transport

(a)

energy

(b)

charge

(c)

momentum

(d)

information

10. A magnetic field is produced by

(a)

a changing electric field

(b)

a moving charge

(c)

both of them

(d)

none of them

11. 5 x 1 = 5

13. (1)

1x10-1m to 1x104m

15. (2)

Solar spectrum

16. Continuous Emission spectra

17. (3)

Spectrum of Carbon Arc

18. Line Absorption spectra

19. (4)

8x10-7 m to 5 x 1Q-3m

20. Fraunhofer Lines

21. (5)

Incandescent solids

2 x 2 = 4
22. Assertion: Electromagnetic waves carries not only energy and momentum but also angular momentum.
Reason : Electromagnetic waves cannot be polarized.
(a) Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Assertion and Reason are true but Reason is the false explanation of the Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.

23. Assertion: Microwaves does not obey reflection and plarization.
Reason: Gamma rays are used in radio therapy for cancer treatment.
(a) Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Assertion and Reason are true but Reason is the false explanation of the Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.

24. 8 x 2 = 16
25. What is displacement current?

26. What are electromagnetic waves?

27. Write down the integral form of modified Ampere’s circuital law.

28. What is meant by Fraunhofer lines?

29. Write the uses of Radio waves.

30. 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.

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

32. What is the orgin of displacement currtent?

33. 5 x 3 = 15
34. Explain the Maxwell’s modification of Ampere’s circuital law.

35. Write down the properties of electromagnetic waves.

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

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

38. Write the uses of Infrared radiation

39. 2 x 5 = 10
40. Compute the speed of the electromagnetic wave in a medium if the amplitude of electric and magnetic fields are 3 × 104 NC-1 and 2 × 10-4 T, respectively.

41. A pulse of light of duration 10−6 s is absorbed completely by a small object initially at rest. If the power of the pulse is 60 × 10−3 W, calculate the final momentum of the object.