Untitled Document

Question Bank No: 1

1. If these were no atmosphere, the average temperature on the surface of the earth would be

a)		lower
b)		higher
c)		same as above
d)		$0^{0} C$

2. Television signal reach us only through the ground waves. The range R related with the transmitter height h is in proportion to

a)		h
b)		h 1/2
c)		h - 1/2
d)		h -1

3. Radio waves do not penetrate in the band of

a)		ionosphere
b)		mesosphere
c)		troposphere
d)		stratosphere

4. Which of the following relation is correct

a)		$\sqrt{ϵ_{o} E_{o}} = \sqrt{μ_{o}} B_{o}$
b)		$\sqrt{μ_{o} ϵ_{o} E_{o}} = B_{o}$
c)		$E_{o} = \sqrt{μ_{o} ϵ_{o}} B_{o}$
d)		$\sqrt{M_{o} E_{o}} = \sqrt{E_{o} B_{o}}$

5. The unit of expression $μ_{0} ϵ_{0}$ are

a)		m/s
b)		$m^{2} / s^{2}$
c)		$s^{2} / m^{2}$
d)		s/m

6. The speed of electromagnetic wave is same for

a)		odd frequencies
b)		even frequencies
c)		all frequencies
d)		all intensities

7. A capacitor of 4 $μ F$ is charged to 20V and then suddenly short circuited by a coil of negligible resistance and inductance 16 $μ H .$ The maximum amplitude of the current oscillations will be

a)		5A
b)		2A
c)		10A
d)		4A

8. Let $[ϵ_{0}]$ denote the dimensional formula of the permittivity of the vacuum and $[μ_{0}]$ of the permeability of the vacuum. If M=mass, L= length, T= time and I= electric current then

a)		$[ϵ_{0}] = M^{- 1} L^{- 3} T^{2}$
b)		$[ϵ_{0}] = M^{- 1} L^{- 3} T^{4} I^{2}$
c)		$[μ_{0}] = ML T^{- 2} I^{- 2}$
d)		$[μ_{0}] = M L^{2} T^{- 1} I$

9. The dimensions of $\frac{1}{2 ϵ_{0}} E^{2} (ϵ_{0} :$ permittivity of free space; E: electric field) is

a)		ML $T^{- 1}$
b)		M $L^{2} T^{- 2}$
c)		M $L^{- 1} T^{- 2}$
d)		M $L^{2} T^{- 1}$

10. Which of the following pairs of space and time varying electric (E) and magnetic (B) fields would generate a plane electromagnetic wave traveling along the X-direction?

a)		$E_{x'} B_{z}$
b)		$E_{y'} B_{z}$
c)		$E_{z'} B_{z}$
d)		$E_{y'} B_{x}$

11. The wavelength of waves transmitted by 50Hz transmission line is

a)		6 $\times 10^{3} m$
b)		6 $\times 10^{4} m$
c)		6 $\times 10^{5} m$
d)		6 $\times 10^{6} m$

12. A parallel plate capacitor consists of two circular plates each of radius 12 cm and seperated by 5.0mm. The capacitor is being charged by external source. The charging current is constant and is equal to 0.15 A. Then of change of potential difference between plates will be

a)		1.873 $\times 10^{7} V / s$
b)		1.873 $\times 10^{8} V / s$
c)		1.873 $\times 10^{9} V / s$
d)		1.873 $\times 10^{10} V / s$

13. Which of the following statements is correct
(i)x-rays is vacuum travel faster than light waves in vacuum
(ii)The energy of X-rays photon is greater than that of a light photon
(iii)Light can be polarised but X-rays cannot

a)		(i) and (ii)
b)		(ii) and (iii)
c)		(i),(ii) and (iii)
d)		(ii) only

14. Which of the following statement is incorrect about electromagnetic waves?

a)		They travel with the same speed in all media
b)		They are produced by accelerating charges
c)		They travel with the velocity of light in vacuum
d)		They transverse in nature

15. An electric field $\vec{E}$ and a magnetic field $\vec{B}$ exist in a region. The fields are not perpendicular to each other

a)		an electromagnetic wave may be passing through the region
b)		an electromagnetic wave is certainly passing through the region
c)		this is not possible
d)		no electromagnetic wave is passing through the region

16. Which of the following is the infrared wavelength?

a)		$10^{- 4}$ cm
b)		$10^{- 5}$ cm
c)		$10^{- 6}$ cm
d)		$10^{- 7}$ cm

17. In an experiment, the electric field was found to oscillate with an amplitude of 18 V/m. The magnitude of the oscillating magnetic field will be

a)		11 $\times 10^{- 11} T$
b)		6 $\times 10^{- 8} T$
c)		9 $\times 10^{- 9} T$
d)		4 $\times 10^{- 6} T$

18. Radio waves detected from distant stars have a wavelength of about 0.20 m. If the speed of the waves is 3 $\times 10^{6} m s^{- 1},$ then the frequency of the waves will be

a)		1.5 $\times 10^{9} Hz$
b)		6.7 $\times 10^{- 9} Hz$
c)		1.5 $\times 10^{4} Hz$
d)		6.7 $\times 10^{- 10} Hz$

19. According to Gauss's theorem of magnetism

a)		$\oint \vec{B}$ . $\vec{ds}$ =q
b)		$\oint \vec{B}$ . $\vec{ds}$ = $\frac{q}{ϵ_{0}}$
c)		$\oint \vec{B}$ . $\vec{ds}$ =0
d)		$\oint \vec{B}$ . $\vec{ds}$ = $\infty$

20. If a source is transmitting e.m. waves of frequency 8.2 $\times 10^{6} c / s .$ then wavelength of these e.m. waves transmitted from the source will be

a)		50.9m
b)		40.5m
c)		42.3m
d)		36.6m

21. The audio waves after being converted into electrical waves cannot be transmitted as such because

a)		they are heavily absorbed by the atmosphere
b)		the height of antenna has to be increased several times
c)		they travel with the speed of sound
d)		the frequency is not constant

22. If $\in_{0} and μ_{0}$ represent the absolute permittance and absolute permeability of free space $\in and μ$ represent the absolute permittiance and absolute permeability of a medium, the refractive index of the medium is given

a)		$\sqrt{\frac{μ_{0} \in_{0}}{\in}}$
b)		$\sqrt{\frac{\in}{μ_{0} \in_{0}}}$
c)		$\sqrt{\frac{\in μ}{\in_{0} μ_{0}}}$
d)		$\sqrt{\frac{\in_{0} μ_{0}}{\in μ}}$

23. A plane electromagenatic wave is incident on a material surface. The waves delivers momentum p and energy E

a)		p $\neq 0, E \neq 0$
b)		p=0, E=0
c)		p=0, E $\neq 0$
d)		p $\neq 0, E = 0$

24. In a plane electromagnetic wave the electric field oscillates sinusoidally at a frequency of 2.5 $\times 10^{10} Hz$ and amplitude 480 V/m. The amplitude of oscillating magnetic field will be

a)		1.6 $\times 10^{- 6} Wb / m^{2}$
b)		1.6 $\times 10^{- 7} Wb / m^{2}$
c)		1.52 $\times 10^{- 8} Wb / m^{2}$
d)		1.52 $\times 10^{- 7} Wb / m^{2}$

25. A plane electromagnetic wave of wave intensity 6 W/ $m^{2}$ strikes a small mirror of area 30 ${cm}^{2} .$ held perpendicular to the approaching wave. The momentum transferred in kg m $s^{- 1}$ by the wave to the mirror per second will be

a)		3.6 $\times 10^{- 8}$
b)		4.8 $\times 10^{- 7}$
c)		1.2 $\times 10^{- 10}$
d)		2.4 $\times 10^{- 9}$

26. The limit of ground wave transmission roughly

a)		1500 MHz
b)		15000 MHz
c)		1500 Hz
d)		1500 kHz

27. The frequency of electromagnetic wave which will be most appropriate to observe a particle of radius 3 $\times 10^{- 4}$ will be of the order of

a)		$10^{15}$
b)		$10^{14}$
c)		$10^{13}$
d)		$10^{12}$

28. Energy stored in a 30 cm length of a laser beans operating at 5 mW is

a)		$10^{- 12} J$
b)		12 $\times 10^{- 12} J$
c)		5 $\times 10^{- 12} J$
d)		5 $\times 10^{- 12} erg$

29. We can produce a displacement current of 1A between the plates of capacitor of 1 $μ$ F by

a)		increasing voltage between the plates at the rate $10^{6} {V_{s}}^{- 1}$
b)		decreasing voltage between the plates at the rate $10^{6} {V_{s}}^{- 1}$
c)		both (a) and (b)
d)		current cannot be produced between the plates of the capacitor

30. If an electromagnetic wave propagating through vacuum is described by
E= $E_{0} \sin (kx - ω t)$
B= $B_{0} \sin (kx - ω t)$ , then

a)		$E_{0} k = B_{0} ω$
b)		$E_{0} B_{0} = ω k$
c)		$E_{0} ω = B_{0} k$
d)		$E_{0} E_{0} = ω / k$

31. Low lying clouds reflect

a)		IR radiations
b)		UV radiations
c)		all radiations
d)		X-ray radiations

32. The unit of $μ_{0} ε_{0}$ is

a)		m/s
b)		$m^{2} / s^{2}$
c)		s/m
d)		$s^{2} / m^{2}$

33. An electromagnetic wave traveling through vacuum represented by E = $E_{0} \sin (kx - ω t)$ . Which of the following is/are independent of the wavelength?

a)		k
b)		k / $ω$
c)		k $ω$
d)		$ω$

34. Given the wave function (in SI units) for a wave to be
$φ$ (x, t) = $10^{3} \sin π (3 \times 10^{6} x - 9 \times 10^{14} t)$
The speed of the wave is

a)		3 $\times 10^{6}$ m/s
b)		3 $\times 10^{7}$ m/s
c)		3 $\times 10^{8}$ m/s
d)		9 $\times 10^{14}$ m/s

35. Ozone layers absorbs radiations of wavelength less than

a)		300 nm
b)		400 nm
c)		500 nm
d)		600 nm

36. Which of the following statements is correct in relation to electromagnetic waves in an isotropic medium?

a)		For a given amplitude of $\vec{E}$ the intensity increases as the first power of frequency f
b)		For a cylindrical wave fronts, the amplitude of the waves varies in proportion to 1/ $r^{2}$ where r is the radius of the wave front
c)		Energy due to electric field is equal to that due to magnetic field
d)		Electric vector $\vec{E}$ and magnetic vector $\vec{B}$ are in plane

37. The sun delivers $10^{3}$ W/ $m^{2}$ of electromagnetic flux to the earth's surface. The total power that is incident on a roof of dimensions 8 m $\times$ 20 m, will be

a)		2.56 $\times 10^{4}$ W
b)		6.4 $\times 10^{5}$ W
c)		4.0 $\times 10^{5}$ W
d)		1.6 $\times 10^{5}$ W

38. In vacuum, the velocity of light does not depend upon

a)		direction of propagation of light
b)		colour of light
c)		speed of source
d)		all of the above

39. For a linearly polarized plane electromagnetic wave :
(i) the electric energy and the magnetci energy have equal average value.
(ii) the electric field and the magnetic field have equal average values

a)		(ii) is false but (i) is true
b)		both (i) and (ii) are false
c)		(i) is false but (ii) is true
d)		both (i) and (ii) are true

40. If the range of the T.V. telecast is to be doubled, then the height of transmitting antenna will have to be

a)		halved
b)		doubled
c)		quardupled
d)		kept unchanged

41. A compass needle is placed between the two parallel plates of a capacitor. The capacitor is connected to source of emf. The compass needle

a)		deflects and remains deflected as long as the battery is connected
b)		deflects for a very short time and then comes back to the original position
c)		deflects and gradually comes to the origincal position in time which is large compared to the time constant
d)		does not deflect

42. A lamp emits monochromatic green light in all directions. If lamp is 3% efficient in converting electrical power to electromagnetic waves and consumes 100 W of poer then amplitude of the electric field associated with the electromagnetic radiation at a distance of 5 m from the lamp will be

a)		2.68 V/m
b)		5.36 V/m
c)		1.34 V/m
d)		4.02 V/m

43. Which of the following pairs of space and time varying electric field E and magnetic field B would generate a plane electromagnetic wave propagating in the Z- direction?

a)		$E_{X}, B_{Z}$
b)		$E_{X}, B_{Y}$
c)		$E_{X}, B_{X}$
d)		$E_{Z}, B_{X}$

44. An electromagnetic wave going through vaccum is described by
E = $E_{0} \sin (kx - ω t)$
and B = $B_{0} \sin (kx - ω t)$

a)		$E_{0} K = B_{0} ω$
b)		$E_{0} ω = B_{0} k$
c)		$E_{0} B_{0} = ω K$
d)		none of these

45. The frequencies of X-rays, $γ$ -rays and ultraviolet rays are respectively a, b and c. Then

a)		a < b, b > c
b)		a > b, b > c
c)		a > b, b < c
d)		a < b, b < c

46. Dimensions of 1/( $μ_{0} ε_{0}$ ) is

a)		$L^{2} / T^{2}$
b)		$T^{2} / L^{2}$
c)		T/L
d)		L /T

47. The minimum wavelength of the emitted x- rays obtained when the accelerating potential difference in x- rays tube at the abode v volt is

a)		eV/ch
b)		hc/eV
c)		eV/h
d)		h/eV

48. Ozone layer in the atmosphere extends from about

a)		10-20 km above the ground
b)		20-50 km above the ground
c)		50-80 km above the ground
d)		80-100 km above the ground

49. Transmission of TV signals from the surface of the moon can be received on earth. But transmitted Tv signals from Delhi cannot be received beyond 100km. The reason is

a)		there is no atmosphere on the moon
b)		there is atmosphere round the earth
c)		TV signal travel in straight line, they donot follow the carvature of the earth
d)		strong gravitational effects

50. Ozone layer is present in the

a)		troposhere
b)		stratosphere
c)		ionosphere
d)		mesosphere