NEET

ALTERNATING CURRENT WS 5
NEET-UG - Physics

m, red light of wavelength 6800 A and radio [4]

0

1. What physical quantity is the same for X-rays of wavelength 10 −10

waves of wavelength 500m?

a) speed b) phase

c) frequency d) energy
2. State the part of the electromagnetic spectrum to which 21 cm wavelength emitted by atomic hydrogen in [4]
interstellar space belongs to?

a) Microwave b) Ultraviolet

c) Visible d) Radio
3. The velocity of light in vacuum can be changed by changing: [4]

a) amplitude b) wavelength

c) None of these d) frequency

4. The electric and the magnetic fields, associated with an e.m. wave, propagating along the + z-axis, can be [4]
represented by

a) [E⃗ = ^ ⃗ ^
E0 k, B = B0 i ] b) ⃗ ^ ⃗ ^
[E = E0 j , B = B0 k]

c) [E⃗ = ^ ⃗ ^
E0 i , B = B0 j ] d) ⃗ ^ ⃗ ^
[E = E0 j , B = B0 i ]

5. The structure of solids is investigated by using [4]

a) infrared radiation b) X-rays

c) cosmic rays d) γ -rays

6. The pressure exerted by an electromagnetic wave of intensity I(Wm-2) on a non-reflecting surface is (c is the [4]
velocity of light):

a) I

c
b) I

c
2

c) Ic2 d) Ic

7. The correct option, if speeds of gamma rays, X-rays and microwaves are vg, ux and vm respectively will be: [4]

a) vg > vx > vm b) vg > vx > vm

c) vg < vx < vm d) vg = vx = vm

8. The amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum is Bo = 510 nT. [4]

Amplitude of the electric field part of the wave is

a) 163 N/C b) 158 N/C

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 c) 153 N/C d) 173 N/C
9. Electromagnetic waves propagate [4]

a) slower in a dielectric b) at the different speed in a dielectric

c) at the same speed in a dielectric d) faster in a dielectric

10. 7.5 MHz to 12 MHz band corresponds to wavelength band of [4]

a) 7.5 m - 12 m b) 25 m - 40 m

c) 50 m - 75 m d) 12 m - 7.5 m
11. The dimensions of (μ are [4]
−1/2
0 ε0 )

a) [LT-1] b) [L-1/2T1/2]

c) [L-1T] d) [L1/2T-1/2]

12. The velocity of light is maximum in [4]

a) Vacuum b) Diamond

c) Glass d) Water
13. State the part of the electromagnetic spectrum to which 1057 MHz (frequency of radiation arising from two [4]
close energy levels in hydrogen known as Lamb shift) belongs to?

a) Ultraviolet b) Microwave

c) Radio d) Visible

14. A linearly polarized electromagnetic wave given as E⃗ = E0 ^i cos (kz - ωt) is incident normally on a perfectly [4]

reflecting infinite wall at z = a. Assuming that the material of the wall is optically inactive, the reflected wave
will be given as

a) E⃗r = -E0 ^i cos (kz + ωt) b) ⃗

Er = -E0 ^i cos (kz - ωt)

c) E⃗r = E0 ^i sin (kz - ωt) d) ⃗

Er = E0 ^i cos (kz + ωt)

15. Light with an energy flux of 18 W/cm2 falls on a non-reflecting surface at normal incidence. The pressure [4]
exerted on the surface is

a) 6 × 10-4 N/m2 b) 2 N/m2

c) 2 × 10-4 N/m2 d) 6 N/m2

16. What is the energy of an ultraviolet photon with a wavelength of 200 nm? [4]

a) 9.339 ×10 −10

J b) 9.739 ×10 −10
J

c) 9.94 ×10 −19

J d) 9.539 ×10 −10
J
17. The speed of electromagnetic waves in a medium of dielectric constant 2.25 and relative permeability 4 is: [4]

a) 3 × 10 8
m/s b) 8
2 × 10 m/s

c) 2.5 × 10 8
m/s d) 8
1 × 10 m/s

18. Using the formula E = hν (energy of a quantum of radiation: photon), the photon energy obtained in units of eV [4]
for λ = 1 mm is

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 a) 1.34 ×10 −3
eV b) 1.54 ×10 −6
eV

c) 1.44 ×10 −6
eV d) 1.24 ×10 −3
eV

19. If a source is transmitting electromagnetic waves of frequency 8.2 × 106 Hz, the wavelength of an [4]

electromagnetic wave transmitted from the source is:

a) 18.8 m b) 58 m

c) 35.6 m d) 42.8 m
20. The electromagnetic waves used in radar systems are: [4]

a) X-rays b) Infrared waves

c) Microwaves d) Ultraviolet rays

21. The electric field part of an electromagnetic wave in a medium is represented by Ex = 0; [4]

Ey = 2.5
N

C
cos[(2π × 10
6 rad

m
) t − (π × 10
−2 rad

s
) x] ; Ez = 0. The wave is

a) moving along x-direction with frequency b) moving along x-direction with frequency

106 Hz and wavelength 200 m 106 Hz and wavelength 100 m

c) moving along y-direction with frequency d) moving along x-direction with frequency
2π × 10
6
Hz and wavelength 200 m 106 Hz and wavelength 200 m
22. In an electromagnetic wave in free space, the root means square value of the electric field is Erms = 6 V/m. The [4]
peak value of the magnetic field is

a) 4.23 × 10-8T b) 1.41 × 10-8T

c) 2.83 × 10-8T d) 0.70 × 10-8T

23. Optical and radio telescopes are built on the ground, but X-ray Astronomy is possible only from satellites [4]
orbiting the earth because

a) Atmosphere reflects X-rays away from earth b) Atmosphere reflects X-rays horizontally so
they don’t reach the earth

c) Atmosphere absorbs X-rays, while visible d) Satellites orbiting the earth make use of
and radio waves can penetrate it. interstellar effects
24. In an electromagnetic wave, the electric and magnetic fields are 100 V/m and 0.265 A/m. The maximum energy [4]
flow will be:

a) 53.0 W/m2 b) 26.5 W/m2

c) 13.2 W/m2 d) 79 W/m2

25. The velocity of electromagnetic waves in free space is 3 × 108 ms-1. The frequency of a radio wave of [4]

wavelength 150 m is

a) 45 MHz b) 2 MHz

c) 2 kHz d) 20 kHz
26. A plane electromagnetic wave travelling along X-axis has a wavelength 10.0 mm. The electric field points along [4]
Y-direction and has peak value of 30 V/m. Then the magnetic field in terms of x in meter and t in second may be

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 expressed as

a) 30 sin 200π (ct - x) b) 30 sin (ct - x)

2π

10

c) 10-7 sin 2π
(ct - x) d) 10-7 sin 200π (ct - x)
10

27. Which of the following are not electromagnetic waves? [4]

a) Cosmic-rays b) β-rays

c) γ -rays d) X-rays
28. An LC circuit contains inductance L = 1μ H and capacitance C = 0.01 μ F. The wavelength of the [4]
electromagnetic wave generated is nearly.

a) 5 m b) 188 m

c) 0.5 m d) 30 m
29. The ratio of the amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave [4]
propagating in a vacuum is equal to

a) the speed of light in vacuum b) the ratio of magnetic permeability to the

electric susceptibility of vacuum

c) reciprocal of speed of light in vacuum d) unity

30. Medical x-rays are taken with electromagnetic waves having a wavelength of around 0.10 nm. What are the [4]
frequency and period of such waves?

a) 20. 4 × 10 15
kHz, 5. 7 × 10
−17
s b) 3 × 10
15
kHz, 3. 3 × 10
−17
s

c) 4. 2 × 10 15 −17
kHz, 2. 8 × 10 s d) 37. 8 × 10
15
kHz, 5. 6 × 10
−17
s

31. A welder wears special glasses to protect his eyes mostly from the harmful effect of [4]

a) ultraviolet rays b) very intense visible light

c) infrared radiation d) microwaves

32. Electromagnetic waves used as a diagnostic tool in medicine are [4]

a) ultrasonic waves b) ultraviolet rays

c) X-rays d) infrared radiation

33. If we want to produce electromagnetic waves of wavelength 500 km by an oscillating charge; then frequency of [4]
oscillating charge must be

a) 15 Hz b) 600 Hz

c) 167 Hz d) 500 Hz
34. In vacuum, the physical property which remains same for microwave of wavelength 1 mm and UV radiation [4]
o

1600A is

a) Speed b) Frequency

c) Magnet d) Wavelength
35. An electromagnetic radiation of frequency ν , wave-length λ , travelling with velocity c in air, enters a glass slab [4]
of refractive index μ . The frequency, wavelength and velocity of light in the glass slab will be respectively

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 a) ν

μ
,
λ

μ
and
c

μ
b) ν,
λ

μ
and
c

c) v, 2 λ and c

μ
d) 2 v
,
λ
and c
μ μ

36. Which wavelength of the sun is used finally as electric energy? [4]

a) Radio waves b) Visible light

c) Infrared waves d) Microwaves

37. The condition under which a microwave oven heats up a food item containing water molecules most efficiently [4]
is

a) the frequency of the microwaves must b) the frequency of the microwaves has no
match the resonant frequency of the water relation with the natural frequency of water
molecules molecules

c) infrared waves produce heating in a d) microwaves are heat waves, so always

microwave oven produce heating
38. The energy of a photon of wavelength 663 nm is [4]

a) 2.0 × 10-20 J b) 5.18 × 10-19 J

c) 3.0 × 10-19 J d) 6.64 × 10-20 J

39. Which of these methods is better to reduce effects of ultra violet light? [4]

a) Untreated eyeglasses b) Full coverage eye protection

c) Plastic lens eyeglasses d) Polycarbonate lens glasses

40. Which of the following radiations has the highest frequency? [4]

a) Microwaves b) Visible light

c) Infrared rays d) X-rays

41. An EM wave radiates outwards from a dipole antenna, with E0 as the amplitude of its electric field vector. The [4]
electric field E0 which transports significant energy from the source falls off as

a) 1

r
b) 1

3
r

c) remains constant d) 1

2
r

42. The correct arrangement of colours in the descending order of their wavelength is: [4]

a) Yellow, Violet, Green, Orange b) Yellow, Green, Orange, Violet

c) Orange, Yellow, Green, Violet d) Violet, Green, Yellow, Orange

43. E
⃗
and B⃗ represent the electric and the magnetic field of an electromagnetic wave respectively. The direction of [4]
propagation of the wave is along

a) E⃗ × B⃗ b) B
⃗

c) B⃗ × E⃗ d) E
⃗

44. In a travelling plane electromagnetic wave, which of the following have zero average value? [4]

a) Magnetic energy and magnetic field b) Electric energy and electric field

c) Magnetic field and electric field d) Magnetic energy and electric energy

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45. The electric field intensity produced by the radiations coming from 100 W bulb at a 3 m distance is E. The [4]
electric field intensity produced by the radiations coming from 50 W bulb at the same distance is

a) E
b) 2E
√2

–
c) √2E d) E

46. Using the formula λ T = 0.29 cmK, the characteristic temperature range obtained for λ
m m
−7
= 5 × 10 m is [4]

a) 5800 K b) 7000 K

c) 6500 K d) 7500 K
47. The conduction current is the same as the displacement current when the source is: [4]

a) neither for d.c. nor for a.c. b) a.c. only

c) both a.c. and d.c. d) d.c. only

48. A linearly polarized electromagnetic wave given as E ^
= E0 i cos(kz − ωt) is incident normally on a perfectly [4]
reflecting infinite wall at z = a. Assuming that the material of the wall is optically inactive, the reflected wave
will be given as

a) E r
^
= E0 i sin(kz − ωt) b) ^
Er = E0 i cos(kz + ωt)

c) E r
^
= − E0 i cos(kz + ωt) d) ^
Er = − E0 i cos(kz − ωt)

49. An electromagnetic wave is produced by a charge [4]

a) moving with a constant speed parallel to a b) moving with an acceleration

magnetic field

c) moving with a constant velocity d) at rest

50. Infrared radiations are detected by: [4]

a) spectrometer b) pyrometer

c) nanometer d) photometer
51. Dimensions of 1/μ 0 ε0 , where symbols have their usual meanings, are: [4]

a) [L2 T-2] b) [L2 T2]

c) [L-1 T] d) [L T-1]

52. Which of the following electromagnetic radiations have the longest wavelength? [4]

a) Microwaves b) γ -rays

c) X-rays d) Radiowaves
53. Displacement current exists only when [4]

a) magnetic field is not changing b) electric field is not changing

c) magnetic field is changing d) electric field is changing

54. A radiation of energy E falls normally on a perfectly reflecting surface. The momentum transferred to the [4]
surface (c = velocity of light) is

a) 2E

c
b) 2E
2
c

c) E
2
d) E

c
c

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55. Radio station WCCO in Minneapolis broadcasts at a frequency of 830 kHz. Wavelength and angular wave [4]
number are

a) 361 m, 0.0174 /m b) 381 m, 0.89 rad/m

c) 391 m, 0.48 rad/m d) 371 m, 0.0245 rad/m

56. The ratio of the magnitudes of the electric field and magnetic field of a plane electromagnetic wave is [4]

a) 1 b) 1

c) 1
2
d) c
c

57. Using the formula λ T = 0.29 cmK, the characteristic temperature range obtained for λ
m m = 10
−6
m is [4]

a) 3100 K b) 3200 K

c) 2900 K d) 3000 K

58. These are three wavelengths 107m, 10-10m, 10-7m. Find their respective names. [4]

a) Visible rays, γ -rays, X-rays b) X-Rays, Visible rays, Radiowaves

c) Radiowaves, X-rays, Visible rays d) X-rays, γ -rays, Visible rays

59. The temperature of an object that emits electromagnetic radiation must be [4]

a) high enough for it to glow b) higher than 0 K

c) higher than that of its surroundings d) higher than 0°C

60. It is necessary to use satellites for long distance TV transmission because [4]

a) Television signals are attenuated by b) Satellites transmit the signals all over the
ionosphere earth

c) Television signals are absorbed by d) Television signals are not properly reflected
ionosphere by the ionosphere
61. What is the amplitude of electric field produced by radiation coming from a 100 W bulb at a distance of 4 m? [4]
The efficiency of bulb is 3.14% and it may be assumed as a point source.

a) 14 × 104 V/m b) 4.2 × 104 V/m

c) 3.43 V/m d) 2.42 V/m

62. Out of the following options which one can be used to produce a propagating electromagnetic wave? [4]

a) An accelerating charge b) A charge moving at a constant velocity

c) A chargeless particle d) A stationary charge

63. The frequency of red light with a wavelength of 4. 2 × 10 −7
m is [4]

a) 7.14 ×10 14
Hz b) 7.34 ×10 14
Hz

c) 7.64 ×10 14
Hz d) 7.94 ×10 14
Hz

64. Light with an energy flux of 25 × 104 Wm-2 falls on a perfectly reflecting surface at normal incidence. If the [4]

surface area is 15 cm2, the average force exerted on the surface is

a) 3.0 × 10-6 N b) 2.50 × 10-6 N

c) 1.25 × 10-6 N d) 1.20 × 10-6 N

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65. A charged particle oscillates about its mean equilibrium position with a frequency of 10 Hz. Frequency of the
9
[4]
electromagnetic waves produced by the oscillator is

a) 600 MHz b) 400 MHz

c) 109
Hz d) 200 MHz
66. The ozone layer blocks the radiation of wavelength [4]

a) more than 3 × 10-7 m b) equal to 3 × 10-7 m

c) all of these d) less than 3 × 10-7 m

67. Electromagnetic waves are transverse in nature. It is evident by: [4]

a) reflection b) interference

c) polarization d) diffraction
68. Which radiations are used in the treatment of muscles ache? [4]

a) ultraviolet b) microwave

c) infrared d) X-rays
69. X-rays are produced when an element of high atomic weight is bombarded by high energy [4]

a) electrons b) neutrons

c) protons d) photons
70. The frequencies of X-rays, γ -rays and ultra violet rays are respectively a, b and c. Then [4]

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

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

71. In general, the wavelength of microwaves is [4]

a) more than that of radiowaves b) less than that of ultra-violet waves

c) more than that of infrared waves d) less than that of infrared waves
72. Which of the following is a natural source of gamma rays? [4]

a) Radio-carbon b) Radio-cobalt

c) Radio-gas d) Radio-phosphorus
73. Long distance radio broadcasts use short-wave bands because [4]

a) Stratosphere reflects waves in these bands b) Troposphere reflects waves in these bands

c) Thermosphere reflects waves in these bands d) Ionosphere reflects waves in these bands
74. The intensity of a plane electromagnetic wave is proportional to [4]

a) Electric field squared b) Electric field cubed

c) 1/ Electric field squared d) Electric field

75. The frequency of γ -rays, X-rays and ultraviolet rays are a, b and c respectively. Then, [4]

a) a < b < c b) a > b > c

c) a = b = c d) a > c > b

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