Download Electromagnetic Waves

(Q.1) Microwaves are electromagnetic waves with
frequency, in the range of
(A) Micro Hertz
(B) Mega Hertz
(C) Giga Hertz
(D) Hertz
(Q.2) Infrared radiation lies adjacent to the low
frequency or long wavelength end of the
visible spectrum. Infrared radiation also plays
an important role in maintaining the earth’s
warmth or average temperature through the:
(A) Energy it carries
(B) Momentum it transferred
(C) The way it heat up the surroundings
(D) Greenhouse effect
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(Q.3) Give the formula for velocity of electromagnetic waves in free
space?
(Q.4) What are microwaves?
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(Q.5) Who was the first person to tell that light is an
electromagnetic
wave?
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(Q.6) What is the source of an electromagnetic wave?
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(Q.7) What is the frequency limit of visible range of
electromagnetic
spectrum in Khz?
(Q.8) What is the name given to that part of
electromagnetic
spectrum which is used in radar?
(Q.9) Which of the following has shortest wavelength?
Microwaves,
ultraviolet rays and X-rays.
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(Q.10) What is the ratio of speed of infrared rays to ultraviolet rays in
vacuum?
(Q.11) An electromagnetic wave is propagating along y-axis. What is
the direction along which oscillations of magnetic field are
taking place?
(Q.12) Name the electromagnetic radiations used for
viewing objects
through haze and fog?
(Q.13) What is the frequency of electromagnetic
radiation to which the
human eye is most sensitive?
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(Q.14) What is the role of ozone in the atmosphere?
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(Q.15) What is the cut off frequency beyond which the
ionosphere
does not reflect electromagnetic radiations?
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(Q.16) What is the ratio of speed of gamma rays and
radiowaves in
vacuum?
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(Q.17) If e0and m0are the electric permittivity and
magnetic
permeability in vacuum, e and m are
corresponding quantities
in medium, then what is the refractive index of
the medium?
(Q.18) The energy of electromagnetic wave in vacuum is
given by the
relation:
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(A)
(B)
(C)
(D)
(Q.19) Let us consider an example of a plane
electromagnetic wave
propagating along z direction. The electric field E
is along the
x-axis and varies sinusoidally with z, at a given
time. What is
the direction of magnetic field ?
(Q.20) When the sun shines on our hand, we feel the
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energy being
absorbed from electromagnetic waves, our hands
get warm but
we do not feel pressure. Why ?
(Q.21) What is average magnetic field of the air plane a
distance of
100 km from a radio transmitter receiving a
signal of power
10.0 micro watts/m2?
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(Q.22) Electric and magnetic fields oscillate sinusoidally
in space and
time in an electromagnetic wave. The oscillating
electric and
magnetic fields
and
are perpendicular to
each other and to
the direction of propagation of the
electromagnetic wave. For a
wave of frequency
, wavelength
propagating along z
direction, E0 and B0 are related as:
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,
(A)
(B)
(C)
(D)
(Q.23) Which of the following law was modified by
Maxwel introducing
Maxwell displacement current?
(Q.24) In an electromagnetic wave, the amplitudes of
magnetic field
Ho and electric field Eo in free space are related
as:
(A) H0 = Eo
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(B)
(C)
(D)
(Q.25) Which of the following are not electromagnetic
waves?
(A) Cosmic rays
(B) Gamma rays
(C) -rays
(D) X-rays
(Q.26) Transmission via sky waves is impossible for the
frequencies:
(A) less than 40 MHz
(B) equal to 40 MHz
(C) more than 40 MHz
(D) all of these
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(Q.27) In an apparatus, the electric field was found to
oscillate with
amplitude of 18 V/m. what is the magnitude of
the oscillating
magnetic field?
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(Q.28) The missing term in Ampere’s circuital law is:
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(A)
(B)
(C)
(D)
(Q.29) Which of the following term acts as a source of
magnetic field
in exactly the same way as conduction current?
(A)
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(B)
(C)
(D)
(Q.30) In the case of steady electric fields in a
conducting wire, which
of the following quantity is zero ?
(A) Conduction current
(B) Magnetic current
(C) Magnetic lines of forces
(D) Displacement current
(Q.31) What is the source of electromagnetic waves?
(A) Stationary charges
(B) Charges in uniform motion
(C) Accelerated charges
(D) Varrying magnetic field
(Q.32) What is the average electric field at the airplane
flying at a distance of 100 km from a radio transmitter
receiving a signal of power 10.0 micro watts/m2 ?
(A) 8.68 ×10–2 V/m
(B) 6.14 ×10–1 V/m
(C) 86.8 ×10–2 V/m
(D) 6.14 ×10–2 V/m
View Answer
(Q.33) A parallel plate capacitor made of circular plates
each of radius R = 5 cm has a capacitance C = 100 pF.
The capacitor is connected to a 220 V a.c supply with
angular frequency of 295 rad s–1. What is the rms value
of the conduction current ?
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(A)
(B)
(C)
(D)
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(Q.34) The dimensions of E/B are same as that of:
(A) Acceleration
(B) Velocity
(C) Charge
(D) Current
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(Q.35) In case of microwave oven, which material is
used as vessels ?
(A) Metal
(B) Steel
(C) Porcelain
(D) Copper
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(Q.36) The microwave oven has an advantage over
conventional heating method as in microwave oven:
(A) Energy is not wasted in heating up the vessel
(B) Porcelain has been used as vessel
(C) Microwave radiation has been used as source
(D) Special vacuum tubes have been used
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(Q.37) Infrared band lies adjacent to the low-frequency
or long-wavelength end of the visible spectrum. Infrared
waves are sometimes referred to as:
(A) Low-frequency waves
(B) Heat waves
(C) Long-wavelength waves
(D) Electromagnetic waves
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(Q.38) The spectrum of electromagnetic wave stretches
over an infinite range of wavelengths. Different regions
are known by different names. The basic difference lies
in their:
(A) Atoms or molecules
(B) Wavelengths or frequencies
(C) Electric or magnetic field
(D) Difference in frequencies with visible light
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(Q.39) A T.V. tower has a height of 100 m. How much
population is covered by the T.V. broadcast if the
average population density around the tower is 10000
km–2? Radius of the earth = 6.40 × 106 m
(A) 40.19 lakhs
(B) 4 lakhs
(C) 40192 lakhs
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(D) 402 lakhs
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(Q.40) An electromagnetic wave of frequency
passes from vacuum into a dielectric
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medium with permittivity
. Then
(A) Wavelength is halved and frequency remains unchanged
(B) Wavelength is doubled and frequency becomes half
(C) Wavelength is doubled and the frequency remains unchanged
(D) Wavelength and frequency both remain unchanged.
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(Q.41) Radio waves of constant amplitude can be
generated with
(A) Filter
(B) Rectifier
(C) FET
(D) Oscillator
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(Q.42) The area to be covered for T.V. telecast is
doubled then the height of transmitting antenna will
have to be
(A) Halfed
(B) Doubled
(C) Quardupled
(D) Kept unchanged
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(Q.43) The electric field vector of a plane
electromagnetic wave oscillates sinusoidally at a
frequency of 4.5 x 1010 Hz. What is the wavelength?
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(Q.44) Find the wavelength of electromagnetic waves of
frequency 5x1019 Hz in free space. Give its two
applications.
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(Q.45) Why is it necessary to use satellite for long
distance T.V. transmission? Give reasons.
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(Q.46) Give four properties of electromagnetic waves.
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(Q.47) A plane electromagnetic wave travels, in
vacuum, along the Y-direction. Write the,
(i) Ratio of the magnitudes of electric and magnetic
field.
(ii) The directions of its electric and magnetic field
vectors.
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(Q.48) Sky waves are not used in transmitting TV
signals. Why? State two factors by which the range of
transmission of TV signals can be increased.
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(Q.49) Explain the following terms:
a) Ground waves.
b) Space waves.
c) Sky waves.
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(Q.50) The TV transmission tower at particular station
has a height of 120 m.
a) What is its covering range?
b) By how much the height of tower should be increased
to double its coverage range?
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(Q.51) What is “Greenhouse effect” for the atmosphere
of earth? Write its importance.
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(Q.52) Suppose that the electric field part of an
electromagnetic wave in vacuum is
={(3.1 N/C) cos
[(1.8 rad/m) y + (5.4 × 106 rad/s)t]} .
(a) What is the direction of propagation?
(b) What is the wavelength λ ?
(c) What is the frequency ν ?
(d) What is the amplitude of the magnetic field part of
the wave?
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(e) Write an expression for the magnetic field part of the
wave.
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(Q.53) Suppose that the electric field part of an
electromagnetic wave in vacuum is
[(1.8 rad/m) y + (5.4 ×
106
={(3.1 N/C) cos
rad/s)t]}
.
(a) What is the direction of propogation?
(b) What is the wavelength λ ?
(c) What is the frequency ν ?
(d) What is the amplitude of the magnetic field part of
the wave?
(e) Write an expression for the magnetic field part of the
wave.
View Answer
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