When plane wave propagates, the wave surface (that is, the equal phase surface of the wave) is a plane electromagnetic wave.
The analysis of plane wave is an analysis method that simplifies 3D wave to 2D wave. This method can characterize the characteristics of electromagnetic wave, but there is no plane wave in practice. Only in the analysis of some far-field problems, 3D electromagnetic wave can be equivalent to 2D plane wave analysis.
The space of wave propagation is called wave field.In the wave field, the ray representing the wave propagation direction is called wave ray, also referred to as wave line.The simplest case is that the vibration of the wave is like a sine function. The locus of the points in the wave field with the same vibration phase at the same time is called the wave surface.The wave front transmitted by the initial vibration state of the wave source at a certain time is called the wave front or wave front, that is, the front wave front.Therefore, there is only one wave front at any time, and there can be any number of wave fronts.If the wave surface is plane, it is plane wave.
Plane wave means that the electric field and magnetic field of electromagnetic wave can be analyzed in one plane.The analysis of plane wave is an analysis method that simplifies 3D wave to 2D wave. This method can characterize the characteristics of electromagnetic wave, but there is no plane wave in practice. Only in the analysis of some far-field problems, 3D electromagnetic wave can be equivalent to 2D plane wave analysis.
The space of wave propagation is called wave field.In the wave field, the ray representing the wave propagation direction is called wave ray, also referred to as wave line.The simplest case is that the vibration of the wave is like a sine function. The locus of the points in the wave field with the same vibration phase at the same time is called the wave surface.The wave front transmitted by the initial vibration state of the wave source at a certain time is called the wave front or wave front, that is, the front wave front.Therefore, there is only one wave front at any time, and there can be any number of wave fronts.If the wave surface is plane, it is plane wave.
Electromagnetic waves radiate from one point to all directions to form a spherical surface. If such waves come from infinity, the spherical surface formed can be regarded as a plane, so it is called a plane wave. In the light wave, the ray is perpendicular to the wave surface, so the ray of the plane wave can be regarded as parallel.
WavefrontIt is a series of parallel plane waves.At a distance from the point wave source, take a local range along the wave propagation direction. The wave surfaces within this range are parallel, and such waves can be approximately regarded as plane waves.Like the sun on the groundlight waveIt can be seen as plane wave.
Uniform plane wave
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A plane wave whose electric field intensity and magnetic field intensity are equal at each point in the wave surface is called a uniform plane wave.When a uniform plane is traveling along the Z or+Z direction, its two pairs of mutually orthogonal electric and magnetic field components are independent of each other.Each pair of electromagnetic field components and propagation direction conform to the right-hand spiral relationship (in the order of electric field, magnetic field and propagation direction), as shown in Figure 1.Therefore, any pair of electric and magnetic fields can form a uniform plane wave.
The wave velocity (also called phase velocity) of a uniform plane wave is related to the characteristics of the medium.In free space, the wave velocity is
There is a simple relationship between the magnitude of electric field and magnetic field:
ηzeroIt is called wave impedance or the intrinsic impedance of the medium.
At any time, the electric energy density and magnetic energy density at any point are equal, accounting for half of the total electromagnetic energy respectively.
For a uniform plane wave, the electromagnetic energy flows along the propagation direction of the wave, and its flow speed is the wave speed v.
Figure 2 shows the distribution of electric field intensity E and magnetic field intensity H along the z-axis of a uniform plane wave along the z-direction at a certain time t.
Wave Number The amount of phase change per unit length of an electromagnetic wave in the direction of propagation.It is usually expressed in k:
In lossless media, for plane waves in time harmonic and steady state, wave number:
In lossy media, the wave number is a complex number.
The ratio of the electric field value to the corresponding magnetic field value in a plane wave with uniform wave impedance.It is usually indicated by the letter η.Because it is related to the characteristics of the medium, it is also called intrinsic impedance.
Incident wave in lossless medium, wave impedance
In free space,
In a conductive medium, the wave impedance will be complex.
