Q.1.
The energy attenuation in optical fibre is mainly due to
-
12%
a)absorption
-
30%
b)scattering
-
44%
c)both a and b
-
14%
d)neither absorption nor scattering
Q.2.
The electromagnetic waves of frequency 2 MHz to 30 MHz are
-
25%
a) in ground wave propagation
-
27%
b) in sky wave propagation
-
32%
c)in micro wave propagation
-
17%
d)in satellite communication
Q.3.
Coaxial cable offers a band width approximately MHz
-
13%
a)1
-
38%
b)20
-
27%
c)250
-
21%
d)1000
Q.4.
Modulation is used to................
-
38%
a) reduce the band width used
-
16%
b) separate the transmission of different areas
-
33%
c) ensure that information may be transmitted to long distance
-
13%
d) allow the use of practical antennas
Q.5.
An antenna can transmit radiation with more efficiency.
-
30%
a)low frequency
-
51%
b) high frequency
-
11%
c)long wave length
-
8%
d)None of these
Q.6.
Which one of the following electromagnetic radiations has the smallest wavelength? [ CBSE-PMT 1994]
-
15%
a)ultraviolet wave
-
17%
b) X-rays
-
34%
c)γ rays
-
34%
d)microwaves
Q.7.
Some scientists have predicted that global nuclear was on the earth would be followed by sever
-
0%
a) rain
-
24%
b) winter
-
12%
c)summer
-
65%
d)radiation hilly rays
Q.8.
Wave length of X-rays lies between
-
26%
a) maximum to finite limites
-
35%
b) minimum to infinite limits
-
32%
c)minimum to certain limits
-
6%
d)inifite to finite limits
Q.9.
The correct sequence of the increasing wavelength of the given radiation sources is
-
35%
a) radioactive source, X-ray tube, crystal oscillator, sodium vapour lamp
-
21%
b) x-ray tube, radioactive source, crystal oscillator, sodium vapour lamp
-
29%
c) X-ray tube, crystal oscillator, radioactive source, sodium vapour lamp
-
15%
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
-
37%
a)reflected by target
-
20%
b) partly absorbed by target
-
27%
c)electromagetic wave
-
17%
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
-
17%
a) sound waves
-
10%
b) light waves
-
45%
c) radio waves
-
28%
d) micro waves
Q.12.
A magnetic field can be produced by
-
19%
a) a moving charge
-
29%
b) a changing electric field
-
3%
c) none of them
-
48%
d) both of them
Q.13.
Transmission via sky waves is possible for the frequencies
-
17%
a) less than 40 MHz
-
30%
b) equal to 40 MHz
-
33%
c) more than 40 MHz
-
20%
d) all of these
Q.14.
Ampere's circutal law is
-
9%
a) consistent
-
33%
b) depends on electric field
-
36%
c) becomes consistent as defined by Maxwell
-
21%
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
-
42%
a)zero
-
42%
b) maximum
-
0%
c)any transient vlaue
-
16%
d)depends on capacitor used
Q.16.
Hydrogen atom does not emit X-ray because
-
19%
a) it has single electron
-
12%
b) it has no neutron
-
19%
c)it has single proton
-
50%
d)its energy levels are two close to each other
Q.17.
The displacement current was first postulated by
-
74%
a) Maxwell
-
3%
b) Marconi
-
16%
c)Ampere
-
6%
d)Hertz
Q.18.
Units of expression µoεo are
-
23%
a) m/s
-
19%
b) m2/s2
-
35%
c) s2 / m2
-
23%
d) s/m
Q.19.
The characteristic impedance of coaxial cable is of the order of
-
13%
a) 50 Ω
-
26%
b) 200 Ω
-
43%
c)270 Ω
-
17%
d)none of the above
Q.20.
The diameter of an optical fiber is
-
21%
a) 10-5 m
-
42%
b) 10-4 m
-
17%
c)10-3 cm
-
21%
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]
-
41%
a)
-
27%
b)
-
18%
c)
-
14%
d)
Q.22.
The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is .. [ CBSE-PMT 2011]
-
55%
a) microwave, infrared, ultravoilet, gamma ray
-
27%
b) gamma rays, ultraviolet, infrared, microwaves
-
14%
c)microwaves, gamma rays, infrared, ultraviolet
-
5%
d)infrared, microwave, ultraviolet, gamma rays
Q.23.
Suppose amplitude of modulated wave equals the signal amplitude, then modulation is
-
37%
a) 0%
-
42%
b) 25%
-
11%
c) 50%
-
11%
d) 100%
Q.24.
Condition underwhich microwave oven heats up a food item containing water molecule most efficiently is
-
27%
a) The frequency of microwave oven must match the resonant frequency of water molecule
-
18%
b) The frequency of microwave has no relation with natural frequency of water molecules
-
32%
c) Microwaves are heat wave so always produce heat
-
23%
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
-
43%
a) 100 km
-
19%
b) 200 km
-
33%
c)300 km
-
5%
d)400 km
Q.26.
What is the direction of E × B in an electromagnetic wave?
-
0%
a)same as that of E
-
4%
b) same as that of B
-
96%
c)same as the direction of propagation of electromagnetic wave
-
0%
d)none of these
Q.27.
The wavelength of x rays is of the order of
-
0%
a)1cm
-
13%
b)1m
-
39%
c)1micron
-
48%
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
-
5%
a) h
-
25%
b) √h
-
25%
c)/ / √h
-
45%
d)1/h
Q.29.
Displacement current is
-
24%
a) continuous when electric field is changing in the circuit
-
20%
b) continuous when magnetic field is changing in the circuit
-
44%
c) continuous in both types of fields
-
12%
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 -----
-
15%
a) moving along x direction with frequency Hz and wave length 100m
-
40%
b) moving along x direction with frequency 106Hz and wave length 200m
-
20%
c) moving along -x direction with frequency 106hz and wave length 200
-
25%
d) moving along y direction with frequency 2π×106Hz and wave length 200m