Electromagnetic Spectrum and Electromagnetic Waves
In this post, we will give you Infor about the electromagnetic spectrum, em spectrum, etc… So let’s Start – We are completely surrounded by electromagnetic radiation in the modern environment.
Have you ever thought of the physics behind these traveling electromagnetic waves?
A bright scientist named Heinrich Hertz was the first to transmit and detect electromagnetic waves. A high voltage current was given to the two ends of two metal wires in his famous experiment, resulting in a spark in the gap between them. Electromagnetic waves were emitted as a result of this spark.
These electromagnetic waves passed through the air and ignited a metal coil more than a meter away. The light would have glowed if you had put an LED in the space. This was a textbook example of electromagnetic wave detection and propagation.
Prior to Hertz, however, the brilliant mathematician James Clerk Maxwell had set the groundwork for electromagnetic radiation by creating mathematical equations. These calculations, together with the Hertz experiment, posed a question.
How do electromagnetic fields detach themselves from wires and propagate through space?
A moving electromagnetic wave, rather than a fluctuating one, is what we require.
Let’s take a logical look at this. Consider the case of an electric charge traveling at a constant rate. The electric field that surrounds it is depicted. Imagine it accelerates for a fraction of a second before continuing its uniform motion at a faster speed.
What we need to know is how this acceleration affects the electric field?
It’s worth noting that information does not travel at an infinite rate; rather, it travels at the speed of light. Similarly, information about a quick change in charge velocity is not sent to the entire electric field region. The field nearby is aware of it, but the field further away is unaware that the charge has accelerated and remains in its previous state.
With the help of two circles, let’s divide these territories. The electric field between these distances must transition because it cannot break. A kink is a name for this transition field. At the speed of light, the kink moves or radiates outwards. To clearly demonstrate the kink animation Image.
Let’s follow the charge with the camera. We can say that the charge’s acceleration resulted in an electromagnetic disturbance or electromagnetic radiation. We shall be able to comprehend the most essential experiment in antenna technology, the oscillating electric dipole, based on this knowledge. This basic oscillating dipole creates electromagnetic radiation in a completely sinusoidal fashion, which is an interesting feature. Let’s have a look.
How it is achieved? Before getting into electromagnetics.
Let’s look at how velocity and acceleration change in this straightforward example. It is self-evident that the velocities at both ends should be zero, and the velocities in the centre should be highest. This indicates that there is a constant rate of acceleration and deceleration. When the chargers are far apart and the velocity is zero, the electric field pattern is drawn here. To gain a better understanding of the situation,
Let’s look at one of the electric field lines in more detail.
Let’s take a look at the electric field line at time t by eight. The electric field line is distorted, as can be seen. This deformity has a simple cause. The region with the greatest acceleration is during this time period. Charges that accelerate or decelerate generate kinks in the electric field, as we observed earlier.
In other words, the old electric field does not adjust well to the new field. Because the charge accelerates at a constant rate, the deformation is continuous. When two charges collide in the center, the distorted line collides as well. It detaches and radiates after that. The speed of light is used to describe this radiation. You can observe that the radiation we produced is precisely sinusoidal in nature if you apply an electric field intensity variation with respect to length. Please keep in mind that this variable electric field will produce a varying magnetic field perpendicular to it.
Let’s look at how this relates to an antenna now. A time-varying voltage is supplied to the metal wire, causing electrons to be moved from right to leave, resulting in positive and negative charges. Positive and negative charges will shuttle back and forth through the wire if the voltage is constantly changing. A dipole antenna is a simple antenna arrangement.
The same radiation is produced by the dipole antenna as in the preceding section. The antenna acts as a transmitter in this scenario. The transmitted signal’s frequency will be the same as the applied voltage signal’s frequency. When the antenna’s functioning is reversed, it can function as a receiver. The oscillating fields of waves create positive and negative charges at the antenna’s ends when propagating electromagnetic waves impact it.
The fluctuating charge accumulation results in a varying voltage signal at the antenna’s core. When the antenna is used as a receiver, this voltage signal is produced. It’s worth noting that the antenna length should be half the wavelength for proper transmission or reception. For proper reception or transmission, this is the initial antenna design criteria. The word “impedance matching” is the second most essential design criteria. Perfect impedance matching ensures that the waves are emitted as efficiently as possible.
The combined effects of resistance, inductance, and capacitance oppose an alternating current as it flows through a circuit. Impedance is the term for this combined impact. According to the maximum power transfer theorem, the load impedance must match the source impedance in order to transfer the maximum amount of power. To gain a better understanding,
Consider a circuit with an alternator as the supply and a motor bulb, for example, as the load. The impedance of the load must match the impedance of the alternator in this setup to obtain optimal power transfer from the alternator to the load. In the case of an antenna system, a comparable impedance balancing is necessary. Because an antenna works with high-frequency signals, the transmission lines’ impedance is crucial. As a result, in order to achieve maximum power.
An antenna’s impedance should also match the impedance of the source and transmission line. If the impedances aren’t identical, some of the power will be reflected back to the source rather than radiating outwards from the antenna. The impedance of free space is 377 ohms. A waveguide is used as a transmission line in a parabolic antenna, and it has a different impedance value than free space. A feedhorn is incorporated in a parabolic antenna for this reason.
The impedance of the wave path is thereby matched to the impedance of empty space, allowing EM waves to be correctly received. We hope this article has clarified the concept of such a significant engineering phenomenon for you, and please remember to support us, thank you.