1, the formation conditions of standing waves
The transmission line terminal is disconnected, short-circuited or impedance mismatch, resulting in the generation of reflected waves. The two waves have the same frequency and propagation speed, but the directions are opposite. When these two conditions are met, a standing wave will be formed.
2. Characteristics of standing wave formation
The vibration period of each point is the same, but the amplitude of each point is different. On the waveform, the positions of nodes and antinodes remain unchanged. Every point in the same node has the same pace, while every point in the adjacent node has the opposite pace. Without the directional propagation of energy, the total energy flow density is zero. In standing waves, energy only changes between antinodes and nodes.
Voltage and current differ by 90 degrees in time and space. This means that current and voltage are perpendicular to each other at a particular moment. The input impedance is pure imaginary, and the resistance varies with the length of the transmission line. This means that in the standing wave, the resistance value is not constant, but varies with the length of the transmission line.
Application of standing wave
1, the propagation of sound waves
Standing wave is one of the core mechanisms of sound wave propagation. In a room or hall, sound waves will reflect back and forth between the wall and the ceiling, forming a standing wave. The superposition of these standing waves determines the sound quality and volume. By understanding the standing wave, we can better design and optimize the sound system and improve the sound quality of music and speeches.
2. Propagation of electromagnetic waves
In electromagnetism, standing wave is the main way of electromagnetic wave propagation in transmission line or waveguide. For example, on the display screen of TV and computer, electrons are transmitted in the form of standing waves in transmission lines, forming the images they see. By understanding and using standing waves, we can develop more efficient and stable electronic equipment.
3. Research on fluctuation phenomenon.
Standing wave is an important tool to study wave phenomenon. Many natural phenomena, such as waves and seismic waves, involve fluctuations. Simplifying these problems into standing waves can be more convenient to understand and solve. In addition, standing waves are also used for research in physics, chemistry, biology and other fields.