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
A.
the frequency of the microwave must match the resonant frequency of the water molecules
It is an electromagnetic wave, therefore the correct choice is (a).
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
X-rays are
electromagnetic radiation
stream of electron
stream of proton
stream of uncharged particle
In gamma ray emission from a nucleus
both the neutron number and the proton number change
there is no change in the proton number and the neutron number
only the neutron number changes
only the proton number changes