Sine waves electromagnetic

The interaction of electromagnetic radiation with matter can be explained using either the electric field or the magnetic field. For this reason, only the electric field component is shown in Figure 10.2. The oscillating electric field is described by a sine wave of the form... 

Figure 12.2 Sine wave representation of electromagnetic radiation. It consists of two in-phase waves, with oscillation of the electric field in the xy plane, and the magnetic field perpendicular to it, in the vz plane.

Figure 1. Sine wave representation of electromagnetic radiation.

The specific absorption rate (SAR) of non-ionizing electromagnetic radiation with frequencies <100 GHz is defined (sine waves, W/kg) as ... 

While an infinitely long sine wave (Fig. 1.2) is the common representation of an electromagnetic wave, it is possible to generate pulses of electromagnetic radiation that last for no more than a few tens of femtoseconds (fs) and which are therefore only a few hundred microns ( rm) in length. This has important implications in photonics. 

James Clerk Maxwell predicted the existence of electromagnetic waves in 1864 and developed the classical sine (or cosine) wave description of the perpendicular electric and magnetic components of these waves. The existence of these waves was demonstrated by Heinrich Hertz 3 years later. 

From Maxwell s equations, the fundamental difference between static near fields (electromagnetic fields) and radiation (electromagnetic waves) is demonstrated. In Section 6.2, we treated the dipole. Consider that the dipole moment varies as a sine function with time. Now if the frequency is very high, the time delay will be noticeable if we are at a distance much longer than the wavelength X = c/f from the dipole. 

The electric field of an electromagnetic wave is usually expressed by an exponential function, mainly because the exponential function is convenient for various calculations, but it is better to express the electric field in the following form by using the cosine and sine functions in order to understand the propagation of the electromagnetic wave. 

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