It has been found that the rainy climate has an absorption effect on radar waves. Later, this principle was used to measure the moisture of the material to make a microwave moisture meter. It uses microwave frequencies of 2.45 GHz (S-band), 8.9-10.68 GHz (X-band), and 20.3-22.3 GHz (K-band). When the microwave passes through a substance containing moisture during transport, a part of the electromagnetic energy is absorbed by the water molecules to attenuate the intensity of the microwave. In the K-band, water molecules will produce molecular resonances, at which the wavelength is 1.35 - 1.5 cm, and electromagnetic waves are transmitted through the waveguide. The microwave moisture meter is mainly composed of a microwave oscillator and a microwave attenuator. The microwave signal is transmitted by the waveguide through the sample to attenuate and receive, and is indicated by the amplifier and the detector. The material to be tested is placed between the transmitter and the receiver. The accuracy of the instrument is ±0.5% of the indicated value (more than 15% of the range); the measuring range of the instrument is 0-1% to 0-70%; this moisture meter is originally used for moisture in soil, cement, walls and other building materials. After measurement, it is used to measure the moisture of various substances such as paper, wood, feed, grain, coal, etc. Microwave refers to electromagnetic waves with a frequency of 300MHz-300GHz. It is an abbreviation for a limited frequency band in radio waves, that is, electromagnetic waves with a wavelength between 1m (excluding 1m) and 1mm, which are decimeter waves, centimeter waves, and millimeter waves. And the general name of the submillimeter wave. The microwave frequency is higher than the general radio wave frequency and is also commonly referred to as "ultra-high frequency electromagnetic wave". Microwave as an electromagnetic wave also has wave-particle duality. The basic properties of microwaves usually appear as three characteristics of penetration, reflection and absorption. For glass, plastic and porcelain, the microwave is almost traversed without being absorbed. For water and food, it absorbs microwaves and heats itself. For metal things, microwaves are reflected. After all, microwave is an electromagnetic wave. When it is used in an instrument, it will cause leakage. People do not know what damage the microwave causes to the human body. Therefore, it is necessary to publicize the damage caused by the microwave to the human body. I. Thermal effect damage: After microwave radiation acts on the living body, part of it is reflected and part of it is absorbed. The absorbed microwave radiant energy is the vibration of the molecules and dielectric dipoles in the tissue, and the sensible friction turns the kinetic energy into thermal energy, causing a temperature rise. The power, frequency, waveform, ambient temperature and the location of the radiation of the microwave radiation have a certain influence on the concentration and the degree of damage. The main hazards are: 3. Cumulative effects: Another characteristic of microwave radiation to biological hazards is its cumulative effect. Generally, after a low-power radiation, it will suffer some insignificant damage and can be recovered after a few days. And long-term work in the microwave, long-term exposure to low-power radiation, can not recover after a month of stopping. However, it must be pointed out that only low-power radiation, high power, long time to do this work, damage will be permanent.
1. Harm the heart;
2, causing eye damage;
Second, the non-thermal effect of microwave radiation damage: the human body is exposed to the microwave radiation environment with little intensity, the body temperature does not increase significantly, but there are often some physiological reactions, mainly in:
1, the role of the nervous system: prolonged exposure to microwave radiation can destroy brain tissue cells, so that cerebral cortical cell activity can be weakened, the formed conditional reflex is inhibited. Repeated microwave radiation may cause nervous system disorders. Some workers who have been exposed to high levels of microwave radiation for a long time have experienced symptoms such as excessive fatigue, headache, shaking hands, increased serum protein, hair loss, and olfactory sensation.
2, the effect of microwave radiation on the blood: long-term exposure to microwave radiation can cause white blood cells and red blood cells in the blood to reduce, and blood coagulation time is shortened.
Therefore, microwave appliances should pay attention to personal protection, when the microwave appliance works, should stay away.