Multiple Choice QuestionsIf E and B represent electric and magnetic field vectors of an electromagentic wave, the direction of propagation of the wave is along
E × B
B × E
E
B
Out of the following statements which is not true ?
Infrared radiations arise due to minor electron transitions in atoms
Infrared radiations are used for long distance photography
Sun is the natural source of infrared radiation
Infrared radiations are detected by using a bolometer
The electric field associated with an electromagnetic wave in vacuum is given by E=i 40 cos (kz-6x108t), where E, z= and t are in volt/m, metre and second respectively. The value of wave vector k is
2 m-1
0.5 m-1
6 m-1
6 m-1
The condition under which a microwave oven heats up a food item containing water molecules most efficiently is
the frequency of the microwave must match the resonant frequency of the water molecules
the frequency of the microwave has no relation with natural frequency of water molecules
microwave are heat waves, so always produce heating
microwave are heat waves, so always produce heating
The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is
gamma rays, ultraviolet, infrared, microwaves
microwaves, gamma rays, infrared, ultraviolet
infrared, microwave, ultraviolet, gamma rays.
infrared, microwave, ultraviolet, gamma rays.
The energy of the EM waves is of the order of 15 keV. To which part of the spectrum does it belong?
X - rays
infrared rays
Ultraviolet rays
Ultraviolet rays
The velocity of electromagnetic radiation in a medium of permittivity 
and permeability 
is given by
The electric and magnetic field of an electromagnetic wave are:
in phase and parallel to each other
in opposite phase and perpendicular to each other
in opposite phase and parallel to each other
in opposite phase and parallel to each other
D.
in opposite phase and parallel to each other
Electromagnetic waves are those waves in which there are a sinusoidal variation of electric and magnetic field vectors at right angles to each other as well as right angles to the direction of wave propagation.
The sinusoidal variation in both electric and magnetic field vectors (
occurs, simultaneously. As a result, they attain the maxima and minima at the same place and at the same time. The amplitudes of the electric and magnetic fields in free spaces are related by
In the figure, electric field vector and
magnetic field vector (
) are vibrating along Y and Z directions and propagation of the electromagnetic wave is shown in X -direction.
Hence, electric and magnetic fields are in phase and perpendicular to each other.
X-rays are
electromagnetic radiation
stream of electron
stream of proton
stream of uncharged particle
Switch
