Q.1
Electromagnetic waves are produced by
  • a)a static charge
  • b)a moving charge
  • c)an accelerating charge
  • d)chargeless particles
Q.2
Maxwells equations are derived from the laws of___________
  • a)electricity
  • b) magnetism
  • c)both electricity and magnetism
  • d)mechanics
Q.3
Which of the following electromagnetic waves has the longest wavelength?
  • a) Radio waves
  • b) Infrared radiations
  • c) x rays
  • d) visible rays
Q.4
Which of the following electromagnetic waves has the highest frequency?
  • a)radio waves
  • b)micro waves
  • c) γ rays
  • d)x rays
Q.5
Dimensional formula of intensity of radiation is _____________
  • a) M1L2T-2
  • b) M1L0T-2
  • c)M1L1T-3
  • d)M1L0T-3
Q.6
The frequency of an electromagnetic wave in free space is 3MHz. When it passesthrough a medium of relative permeability εr=4.0 , then its frequency
  • a) becomes half
  • b) become doubled
  • c) remain same
  • d) become √2 times
Q.7
The frequency of electromagnetic wave having wavelength 25mm is _________ Hz
  • a)1.2 ×1010
  • b) 7.5 ×105
  • c)1.2 ×108
  • d)7.5 ×106
Q.8
Unit of energy density of electromagnetic wave is _________
  • a)Jm-3
  • b)Jm-2
  • c)wm-2
  • d)None of these
Q.9
What is the ratio of velocities of light rays of wavelengths 40000 Å and 80000 Å in vaccum ?
  • a)1:2
  • b) 1:1
  • c)2:1
  • d)cannot be determined
Q.10
Which of the following rays are not electromagnetic waves?
  • a) α rays
  • b) β rays
  • c) γ rays
  • d) heat rays
Q.11
A plane electromagnetic wave of frequency 25MHz travels in free space along thex direction. At a particular point in space and time E=6.3jVm-1 then Bat this point is__________
  • c)1.89× 109 k T
  • a)2.1 × 10⁻⁸ i T
  • b)2.1 × 10⁻⁸ k T
  • d)2.52× 10⁻⁷ k T
Q.12
Light with an energy flux of w/m3 falls on a non-reflecting surface atnormal to surface. If the surface has an area of 20m2 . The average force exertedon the surface during 30 minutes is________
  • a)6.48×105 N
  • b)3.60×102 N
  • c)1.2×10⁻⁶ N
  • d)2.16×10⁻³N
Q.13
Energy density of an electromagnetic wave of intensity 0.02 Wm-2 is _______
  • b)6×106 Jm-3
  • c)1.5×1010 Jm-3
  • d)none of the above
  • a) 6.67×10⁻¹¹ Jm-3
Q.14
The waves used in communication are generally called
  • a)γ ray
  • b) α ray
  • c) microwaves
  • d)radiowave
Q.15
For an electromagnetic wave, the phase difference between vectors E and B (faraway from the source)
  • a) 0
  • b) π /2
  • c) π
  • d) 3π/2
Q.16
The electric and magnetic field of an electromagnetic wave are
  • a) in phase and perpendicular to each other
  • b)in phase and parallel to each other
  • c) in opposite phase and perpendicular to each other
  • d) in opposite phase and parallel to each other
Q.17
Unit of µo C is same as that of
  • a)current
  • b)resistance
  • c) electric charge
  • d) velocity
Q.18
If the direction of magnetic field B at some instant is along +ve Z direction and the electromagnetic wave is propagating along +ve X direction, then the direction of electric field E at that instant is_________
  • a) along -ve Y direction
  • b) along +ve Y direction
  • c) along +ve X direction
  • d) along -ve X direction
Q.19
The velocity of light in vaccum can be changed by changing____
  • a) frequency
  • b)wavelength
  • c) amplitude
  • d) none of these
Q.20
Which of the Following is not a component of communication System ?
  • a) Transmitter
  • b) Transmission channel
  • c) Noise
  • d) Receiver
Q.21
An electromagnetic wave going through vaccum is described by E=Eo sin(kx- ω t) then B=Bo sin(kx- ω t) then
  • a) EoBo= ω k
  • b) Eok = Bo ω
  • c) Eo ω = Bok
  • d) none of these
Q.22
If the wavelength of light is 40000 A then the number of waves in 1mm length will be___
  • a) 2.5
  • b) 2500
  • c) 250
  • d) 25000
Q.23
The SI unit of displacement current is_________
  • a) coulomb
  • b) henry
  • c) ampere
  • d) faraday
Q.24
The electromagnetic waves do not transport_______
  • a)energy
  • b)charge
  • c)momentum
  • d)information
Q.25
The frequency 1057MHz of radiation arising from two close energy levels inhydrogen belongs to_____
  • a) radio waves
  • b)infrared waves
  • c)micro waves
  • d)γ rays
Q.26
Maxwell’s modified form of Ampere’s circuital law is____
  • a)
    ch-20_qn-211choice_img_no1.png
  • b)
    ch-20_qn-211choice_img_no2.png
  • c)
    ch-20_qn-211choice_img_no3.png
  • d)
    ch-20_qn-211choice_img_no4.png
Q.27
The wavelength of x rays is of the order of
  • a) 10–3 m
  • b) 10–5 m
  • c) 10–10 m
  • d) 10–12 m
Q.28
A point source of electromagnetic radiation has an average output power of 800W.The maximum value of electric field at a distance of 4.0m from the source is
  • a)64.7V/m
  • b)57.8V/m
  • c)56.72V/m
  • d)54.77V/m
Q.29
A plane electromagnetic wave Ez=100cos(6 ×108t + 4x) V/m propagate in a medium of refractive index
  • a) 1.5
  • b) 2.0
  • c)2.4
  • d)4.0
Q.30
An observer is at 2m from an isotropic point source of light emitting 40w power.The rm.s value of electric due to the source at the position of the observeris_____
  • b) 17.3 V/m
  • d) 1.73
  • a) 5.77 × 10⁻⁸ V/m
  • c) 57.7 × 10⁻⁸
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