Introduction to electromagnetic radiation and electromagnetic waves

A radio wave is an electromagnetic wave. The number of times an electromagnetic wave vibrates per second is called the frequency (in Hertz Hz); the distance traveled per second is called the speed (in meters per second); the distance traveled in each cycle is called the wavelength (in terms of Meter). Electromagnetic waves have a wide spectrum range, and the radio spectrum is only a small part of them. At present, humans cannot develop and utilize the frequency band above 3000 GHz. Therefore, although the radio frequency is a natural resource shared by human beings, the spectrum resources are limited relative to a certain time, space, location, and the radio spectrum is the precious natural resource of the country like minerals, water, forests, mountains and grasslands.

In recent years, the demand for radio services in society has increased dramatically. To meet this demand, various radio services have emerged. There are many radio transmitters installed in urban and rural areas of our city, and these devices are often close to residential houses. The public is gradually concerned about the health damage caused by exposure to radio frequency electromagnetic radiation.

Electromagnetic radiation consists of electrical energy and magnetic energy that are collectively transferred by space, and this energy is generated by the movement of charge; for example, the mobile charge emitted by the RF antenna that is transmitting the signal generates electromagnetic energy.

The electromagnetic spectrum includes a wide range of electromagnetic radiation, from extremely low frequency electromagnetic radiation to extremely high frequency electromagnetic radiation. There are also radio waves, microwaves, infrared rays, visible light and ultraviolet light. The general definition of the radio frequency portion of the electromagnetic spectrum refers to radiation having a frequency of from about 3 kHz to 300 GHz.

The energy derived from electromagnetic radiation depends on the frequency of the frequency - the higher the frequency, the greater the energy. Extremely high X-rays and gamma rays produce large amounts of energy that can destroy molecules that synthesize human tissue. In fact, the energy of X-rays and gamma rays is enough to ionize atoms and molecules, so they are classified as "ionizing" radiation. Although these two types of radiation are used for medical purposes, excessive exposure will impair health. The electromagnetic energy generated by X-rays and gamma rays is different from the electromagnetic energy generated by RF transmitters. The electromagnetic energy of the radio frequency device belongs to the lower frequency end of the spectrum, and cannot be broken into chemical bonds that bind the molecules together, so it is classified as "non-ionizing" radiation.

There are many sources of electromagnetic radiation. Both inside and outside the human body are covered with electrical and magnetic energy emitted by natural and artificial sources of radiation; lightning is one example of a natural source of radiation. As for artificial radiation sources, microwave ovens, radios, television broadcast transmitters, and satellite communication devices are included. An article on the possible health effects of RF radiation over the past few decades has led to a lot of research. However, the results of the reports are often contradictory and cannot lead to affirmative conclusions. Many independent and authoritative research groups have found no substantial scientific evidence that radiofrequency radiation can endanger health.

For the sake of safety, the International Guidelines for Non-Ionizing Radiation Protection Committee published by ITU in 1998 set a safety ceiling for human exposure to radio frequency electromagnetic fields up to 300 GHz to protect staff and the public. Damaged by non-ionizing radiation.

It is understood that the Hong Kong Telecommunications Authority commissioned a consultancy firm in 1996 to study the safety of electromagnetic radiation emitted by telecommunications launchers. The results of the study pointed out that there are many radio transmitters on the roof of some buildings in Hong Kong, but even if they live in these buildings, it is absolutely safe. The study found that the level of electromagnetic radiation exposed within the general reach of residential units and rooftops is much lower than the safety ceiling set by the International Commission on Non-Ionizing Radiation Protection.

Since the power of the cellular phone is low, it is not a source of harmful radiation under normal use conditions. Many studies have also pointed out that there is no evidence that cellular phones can be harmful under normal use.

The electromagnetic wave is a transverse wave that can be used for detection, positioning, communication, and the like. The electromagnetic spectrum is radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X-rays (X-rays), gamma rays.

application:

â—†Radio waves for communication, etc.

â—†Microwave for microwave oven

â—†Infrared is used for remote control, thermal imager, infrared guided missile, etc.

â—† Visible light is the basis for all creatures to observe things

â—†UV is used for medical disinfection, verification of counterfeit banknotes, measurement distance, engineering flaw detection, etc.

â—†X-ray for CT photography

â—†Gamma rays are used for treatment to make atoms transition to generate new rays, etc.

â—† Radio waves. Both radio and television use electromagnetic waves. In radio broadcasting, people first convert sound signals into electrical signals, and then carry these signals from high-frequency oscillating electromagnetic waves to the surrounding space. In another location, after receiving the electromagnetic waves, the receiver restores the electrical signals into sound signals. This is the general process of wireless broadcasting. In television, in addition to processing sound signals as in wireless broadcasting, the optical signals of the images are also converted into electrical signals, and then the two signals are also transmitted together by high-frequency oscillating electromagnetic waves to the surrounding space. After receiving the electromagnetic waves, the television receiver restores the electrical signals to sound signals and optical signals, thereby displaying the television screen and the sound in the speaker.