Αποτελέσματα Αναζήτησης
The distance between successive wavefronts at 2π phase intervals is λo in the direction of propagation, and the distances separating these same wavefronts as measured along the x and z axes are equal or greater, as illustrated in Figure 9.2.1. For example: λ z = λo cos θ = 2π kz ≥ λo.
Let’s say z is the vertical direction (towards the sky), so the sky above us is the x-y plane. Let’s say the sun is in the x direction. Thus plane waves from the sun have k in the xˆ direction and are polarized in the y-z plane. Thus, the sky molecules can only get pushed in the y and z directions from sunlight.
That is why we call these waves transverse electromagnetic (TEM) waves. We consider the electric field of a monochromatic electromagnetic wave with frequency ω and electric field amplitude E0, which propagates in vacuum along the z-axis, and is polarized along the x-axis, (Fig. 2.1), i.e. | k k| = ez, and e( k)= e x. ThenweobtainfromEqs.(2. ...
The simplest representation of Maxwell’s equations is in differential form, which leads directly to waves; the alternate integral form is presented in Section 2.4.3. The differential form uses the vector del operator ∇: ∇ ≡ xˆ ∂ + ∂x yˆ ∂ ∂ ∂y. + zˆ ∂z.
In order to satisfy all four equations, the waves must have the E and B fields transverse to the propagation direction. Thus, if the wave is traveling along the positive z-axis, the electric field can be parallel to the +x-axis and B-field parallel to +y. Half a cycle later, E and B are parallel to –x and –y.
An electromagnetic wave that is travelling in the positive z-direction with its electric field oscillating parallel to the x-axis and its magnetic field oscillating parallel to the y-axis (as shown in Figure 28.1) can be represented mathe-matically using two sinusoidal functions of position (z) and time (t): . max.
It describes the trajectory of a point of coordinates x(t) and y(t) (these are normalized ex ( t ) and e y ( t ) values) along an ellipse. As time flows, the point moves along the ellipse with an angular frequency ω , i.e., in one period, T = 2 π / ω , the point completes one elliptical trajectory.
