It is well known that light is transverse wave and the angle between the electric field and magnetic field is 90 degree for all light. However the phase difference between the fields has been shown 0 degree or 90 degree in different books. What is the actual fact?
E and H are in phase (0 degrees difference) for light, and for all electromagnetic waves. E and H can be at other phases in places where more energy is stored than is transmitted, for example close to some antennas, coils or capacitors. E and H differing in phase by 90 degrees represents stored energy. In a resonant circuit energy is stored between the plates of a capacitor, then in the magnetic field of the circuit feeding it. This happens twice every cycle.
The electric and magnetic fields are always in-phase if the wave can be treated as a plane wave, and in vacuum or any medium with linear response, such as air.The quarter wave plate accepts linearly polarized light at some angle wrt the fast axis of the QWP; the orthogonal components of the electric field vector under go different amounts of optical delay, resulting in two distinct electromagnetic waves, with the same phase delay in their electric and magnetic fields
Dear Md
welcome,
There is a similar question in research gate and i gave this answer:
The electric and the magnetic field form the electromagnetic wave which is dynamic travelling with speed of light in space. The two fields are coupled with each other when one grows the other grows and when it is attenuated the other is attenuated. In fact the magnetic field represents the kinetic energy in the wave while the electric field represents the potential energy in the wave. During the propagation, one form is transferred to the other alternately. If you annihilate one form the other will be be also finished.
Mathematically we express the fields of the electromagnetic wave in free space as:http://hyperphysics.phy-astr.gsu.edu/hbase/Waves/emwv.html
Ex= Em cos ( wt - 2pi z/ lambda),
Hy= Hm cos (wt - 2pi z/ lambda)
Em/Hm = Zw where Zw is the wave impedance.
w is the frequency, lambda is the wavelength of the wave,
According to this formulation E and H are perpendicular to each other in space. They have the same phase in time wt.
If the electromagnetic wave is propagating in a lossy medium, the wave impedance will be complex, this means that there will be some form of phase shift between E and H.
The link is:https://www.researchgate.net/post/Time_Phase_between_E_and_H
Best wishes
There is very nice illustration of plane wave at https://en.wikipedia.org/wiki/Electromagnetic_radiation showing the phase of E and H fields. You can trust it. In a standing wave, phases of E and H differ by 90 deg., because the reactive power appears in a standing wave.
- Badges
- Science topic
- Similar topics
- Books