Q.1
The energy attenuation in optical fibre is mainly due to
  • a)absorption
  • b)scattering
  • c)both a and b
  • d)neither absorption nor scattering
Q.2
The electromagnetic waves of frequency 2 MHz to 30 MHz are
  • a) in ground wave propagation
  • b) in sky wave propagation
  • c)in micro wave propagation
  • d)in satellite communication
Q.3
Coaxial cable offers a band width approximately MHz
  • a)1
  • b)20
  • c)250
  • d)1000
Q.4
Modulation is used to................
  • a) reduce the band width used
  • b) separate the transmission of different areas
  • c) ensure that information may be transmitted to long distance
  • d) allow the use of practical antennas
Q.5
An antenna can transmit radiation with more efficiency.
  • a)low frequency
  • b) high frequency
  • c)long wave length
  • d)None of these
Q.6
Which one of the following electromagnetic radiations has the smallest wavelength? [ CBSE-PMT 1994]
  • a)ultraviolet wave
  • b) X-rays
  • c)γ rays
  • d)microwaves
Q.7
Some scientists have predicted that global nuclear was on the earth would be followed by sever
  • a) rain
  • b) winter
  • c)summer
  • d)radiation hilly rays
Q.8
Wave length of X-rays lies between
  • a) maximum to finite limites
  • b) minimum to infinite limits
  • c)minimum to certain limits
  • d)inifite to finite limits
Q.9
The correct sequence of the increasing wavelength of the given radiation sources is
  • a) radioactive source, X-ray tube, crystal oscillator, sodium vapour lamp
  • b) x-ray tube, radioactive source, crystal oscillator, sodium vapour lamp
  • c) X-ray tube, crystal oscillator, radioactive source, sodium vapour lamp
  • d) radioactive source, X-ray tube, sodium vapour lamp, crystal oscillator
Q.10
X -ray are not used for radar purpose because they are not
  • a)reflected by target
  • b) partly absorbed by target
  • c)electromagetic wave
  • d)completly absorbed by target
Q.11
A radar sends the waves towards a distant object and receives the signal reflected by object. These waves are
  • a) sound waves
  • b) light waves
  • c) radio waves
  • d) micro waves
Q.12
A magnetic field can be produced by
  • a) a moving charge
  • b) a changing electric field
  • c) none of them
  • d) both of them
Q.13
Transmission via sky waves is possible for the frequencies
  • a) less than 40 MHz
  • b) equal to 40 MHz
  • c) more than 40 MHz
  • d) all of these
Q.14
Ampere's circutal law is
  • a) consistent
  • b) depends on electric field
  • c) becomes consistent as defined by Maxwell
  • d) depends on type of magnetic field
Q.15
The conduction current in ideal case through a circuit is zero when charge on capacitor is
  • a)zero
  • b) maximum
  • c)any transient vlaue
  • d)depends on capacitor used
Q.16
Hydrogen atom does not emit X-ray because
  • a) it has single electron
  • b) it has no neutron
  • c)it has single proton
  • d)its energy levels are two close to each other
Q.17
The displacement current was first postulated by
  • a) Maxwell
  • b) Marconi
  • c)Ampere
  • d)Hertz
Q.18
Units of expression µoεo are
  • a) m/s
  • b) m2/s2
  • c) s2 / m2
  • d) s/m
Q.19
The characteristic impedance of coaxial cable is of the order of
  • a) 50 Ω
  • b) 200 Ω
  • c)270 Ω
  • d)none of the above
Q.20
The diameter of an optical fiber is
  • a) 10-5 m
  • b) 10-4 m
  • c)10-3 cm
  • d)10-2 cm
Q.21
The velocity of electromagnetic radiation in a medium of permitivity εo and permiability µo is given by.. [ CBSE-PMT 2008]
  • a)
    ch-20_qn-22choice_img_no1.png
  • b)
    ch-20_qn-22choice_img_no2.png
  • c)
    ch-20_qn-22choice_img_no3.png
  • d)
    ch-20_qn-22choice_img_no4.png
Q.22
The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is .. [ CBSE-PMT 2011]
  • a) microwave, infrared, ultravoilet, gamma ray
  • b) gamma rays, ultraviolet, infrared, microwaves
  • c)microwaves, gamma rays, infrared, ultraviolet
  • d)infrared, microwave, ultraviolet, gamma rays
Q.23
Suppose amplitude of modulated wave equals the signal amplitude, then modulation is
  • a) 0%
  • b) 25%
  • c) 50%
  • d) 100%
Q.24
Condition underwhich microwave oven heats up a food item containing water molecule most efficiently is
  • a) The frequency of microwave oven must match the resonant frequency of water molecule
  • b) The frequency of microwave has no relation with natural frequency of water molecules
  • c) Microwaves are heat wave so always produce heat
  • d) Infrared waves produces heta in microwave ovan
Q.25
An electric charge oscillating with a frequency of 1 kilo cucles/ second can radiate electromagetic waves of wavelength
  • a) 100 km
  • b) 200 km
  • c)300 km
  • d)400 km
Q.26
What is the direction of E × B in an electromagnetic wave?
  • a)same as that of E
  • b) same as that of B
  • c)same as the direction of propagation of electromagnetic wave
  • d)none of these
Q.27
The wavelength of x rays is of the order of
  • a)1cm
  • b)1m
  • c)1micron
  • d)1angstrom
Q.28
Televison signals reach us only through the ground waves. the range R related with the transmitter height h is in proportion to
  • a) h
  • b) √h
  • c)/ / √h
  • d)1/h
Q.29
Displacement current is
  • a) continuous when electric field is changing in the circuit
  • b) continuous when magnetic field is changing in the circuit
  • c) continuous in both types of fields
  • d) continuous through wires and resistance only
Q.30
The electric field part of an electromagnetic wave in a medium is represented by Ex Ey Ey=2.5 cos[(2π×106)t - (π×10-2) x] The wave is -----
  • a) moving along x direction with frequency Hz and wave length 100m
  • b) moving along x direction with frequency 106Hz and wave length 200m
  • c) moving along -x direction with frequency 106hz and wave length 200
  • d) moving along y direction with frequency 2π×106Hz and wave length 200m
0 h : 0 m : 1 s