Q.1
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.2
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.3
The SI unit of displacement current is_________
  • a) coulomb
  • b) henry
  • c) ampere
  • d) faraday
Q.4
The electromagnetic waves do not transport_______
  • a)energy
  • b)charge
  • c)momentum
  • d)information
Q.5
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.6
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.7
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.8
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.9
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.10
A plane electromagnetic wave of wave intensity 10 wm-2 strikes a small mirror ofarea 20 cm2 , held perpendicular to the approaching wave. The radiation force onthe mirror will be
  • a)6.6×10-11 N
  • b)1.33×10-11 N
  • c)1.33×10-10 N
  • d)6.6×10-10 N
Q.11
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_____
  • a) 5.77 × 10-8 V/m
  • b) 17.3 V/m
  • c) 57.7 × 10-8
  • d) 1.73
Q.12
The instrument/ equipment which transform one form of energy into another form of energy is called a _______
  • a)transponder
  • b) transducer
  • c)receiver
  • d)transmitter
Q.13
Which of the following are modulation techniques for digital communication?
  • a) ASK
  • b) FSK
  • c)PSK
  • d)All of them
Q.14
What is the main function of transponder
  • a) To amplify the signal
  • b) To change its frequency
  • c)Both (a) and (b)
  • d)none of them
Q.15
Electromagnetic waves used in medicine to destroy cancer cells
  • a) radio waves
  • b) infrared rays
  • c) gamma rays
  • d) ultraviolet rays
Q.16
In electromagnetic spectrum, the visible light lie between
  • a)radiowaves and microwaves
  • b) ultraviolet rays and infrared rays
  • c)ultraviolet rays and x rays
  • d)infrared rays and microwaves
Q.17
Which of the following statements is not true in case of electromagnetic waves?
  • a)they are light waves
  • b)they are transverse waves
  • c)propagates through space
  • d)they are longitudinal waves
Q.18
In an electromagnetic wave in free space, the direction of electric field vector E is along y axis and magnetic field vector B is along z axis then which of the following is true
  • a)(E × B) × E=1
  • b)(E × B) × B=1
  • c)(E × B) × B=0
  • d)none of these
Q.19
When a plane electromagnetic wave travels in vacuum, the average electric energydensity is given by (Eo is the amplitude of the electric field)
  • a)
    ch-20_qn-224choice_img_no1.png
  • b)
    ch-20_qn-224choice_img_no2.png
  • c)
    ch-20_qn-224choice_img_no3.png
  • d)
    ch-20_qn-224choice_img_no4.png
Q.20
In a plane electromagnetic wave , the electric field oscillates sinusoidaly at a frequency of 2.0×1010Hz. if the peak value of electric field is 60V/m the average energy density (in Jm-3) of the magnetic field of the wave will be
  • a)2π×10-7
  • b) 10-7 / 2π
  • c)4π×10-7
  • d) 10-7 / 4π
Q.21
If the earth were not having atmosphere, its temperature________.
  • a)would have been low
  • b)would have been high
  • c)would hav remain constant
  • d)none of these
Q.22
_________ is responsible for the green house effect
  • a) infrared rays
  • b) ultraviolet rays
  • c)x raya
  • d)radiowaves
Q.23
When an electromagnetic wave encounters a dielectric medium, the transmittedwave has
  • a) same frequency but different amplitude
  • b) same amplitude but different frequency
  • c) same frequency and amplitude
  • d) different frequency and amplitude
Q.24
An electromagnetic wave
  • a)can be deflected by electric field
  • b)can be deflected by magnetic field
  • c)can be deflected bye both electric and magnetic field
  • d)none of these
Q.25
The potential difference between the plates of a parallel plate capacitor is chargingat the rate of 106V/s . If the capacitance is 2µF . The displacement current inthe dielectric of the capacitor will be
  • a)4A
  • b)3A
  • c)2A
  • d)1A
Q.26
What should be the minimum length of the antenna capable of emitting audio signal ofwave length λ ?
  • a)λ/4
  • b) λ/8
  • c)λ/2
  • d)λ
Q.27
_________is used as a medium an space communication
  • a) Two wire line
  • b) Space
  • c) Amplifier
  • d) Optical fibre
Q.28
The band width of Audio signal is
  • a)20 HZ
  • b)20 KHZ
  • c)20 MHz
  • d)20 GHz
Q.29
ground waves are polarized at direction.
  • a)vertically upward
  • b)horizontal
  • c)tangential direction to the surface of the earth
  • d)in all four.
Q.30
Intensity of electric field of ground waves is in of the distance travelled by it.
  • a) Square
  • b) inverse of root
  • c)proportion
  • d)inverse
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