Many have heard the expression UHF more than once, seen these letters on different devices or instructions for them. However, not everyone knows what this abbreviation means. A detailed interpretation of microwave frequency will help to better understand the essence of this term and find out in which areas it is most often used.
Content
- Super high frequency
- Satellite communications and radar
- Household use
- The device and principle of operation of the microwave
Super high frequency
Literally abbreviated expression stands for ultra-high frequency. For a layman, these words may seem incomprehensible. To better understand what microwave means, you must have at least a minimum of knowledge from the field of physics. This science studies different types of electromagnetic radiation:
- super long (radio waves);
- terahertz;
- infrared;
- optical;
- ultraviolet;
- hard and x-ray.
Ultra-high frequency waves occupy the space between the infrared far-frequency and ultra-high frequencies. Their length forms a wide range from one millimeter to thirty centimeters. In comparison with ultra-long radio waves, the length of which is measured in hundreds of meters, the size of microwave waves is extremely small, therefore they are also called the centimeter or decimeter range. In foreign literature, microwave radiation is commonly referred to as microwave radiation.
The peculiarity of ultra-high frequency waves is that they combine the properties inherent in both light radiation and radio waves. For example, just like rays of light, microwave waves are able to reflect, focus, and propagate in a straight line.
Satellite communications and radar
Another similarity of such radiation with light rays is the ability to transmit information in a high density mode. T. e. one ultra-high frequency beam can broadcast up to a thousand telephone conversations. This property made it possible to successfully apply microwave radiation:
-
In radar. The essence of the use of microwave in radar equipment lies in the fact that launched into space are short and intense pulses are partially reflected from distant objects, return and are recorded by special instruments. Interest in such a technique for detecting objects arose during the Second World War, when the question of search was extremely acute. - In commercial lines of communication. The advantage of using ultra-high frequency beams in this area is the path of their propagation. Unlike other waves used to provide communication, microwave frequencies do not travel along the line of the earth's surface, which has many irregularities, but in a straight line from one relay station to another. In order for the signal to be transmitted quickly and efficiently, such stations are located at a high altitude every 50 km. Arrangement of commercial lines is quite expensive, but the price is fully compensated by low power consumption and high information capacity of communication channels.
Another area where effective microwave waves are used - this is satellite communication. On land, it is provided by a system of radio towers that broadcast signals over long distances. In the case of intercontinental negotiations, the role of repeaters is performed by artificial satellites located in the geostationary orbit of the Earth. Each satellite concentrates thousands of communication channels, guaranteeing the simultaneous transmission of high-quality telephone and television signals to users of modern devices.
Household use
Surely everyone who at least once thought about what microwave means, how this expression is deciphered, immediately remembered about a microwave oven. This device is perhaps the most famous example of the use of ultra-high frequency waves in the home. It is based on the thermal effect of microwave waves.
This property was accidentally discovered by the American physicist Percy Spencer back in 1942. As a result, three years later, the scientist received a patent for the use of radiation in the cooking process. A couple of years later, a device weighing more than 300 kg appeared in military hospitals and canteens, which is the prototype of a modern microwave. For several decades, the device has changed significantly. A microprocessor control system was built into it, and a revolving table appeared. Modern models have the ability to connect to the Internet.
Despite all the modernizations and modifications, the main advantage of the microwave oven has been and remains the speed of heating and cooking. This speed is provided due to the thermal effect of microwaves not only on the surface, but on the entire volume of the product.
The device and principle of operation of the microwave
The microwave oven is not overly complicated. Its construction consists of:
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Metal chamber. Products for cooking are placed in it. - Microwave emitter (magnetron).
- Transformer. It provides the magnetron with a high voltage power supply.
- Waveguide. Through it, radiation from the magnetron is transmitted to the camera.
Uniform heating of food in the oven is ensured by rotating a special table. The built-in fan helps to avoid overheating during operation, electronic circuits make the microwave control as convenient and safe as possible.
Products placed in a metal chamber are heated by exposure to powerful beams with a frequency of 2450 MHz. Penetrating inside to a depth of about 3 cm, these rays set in motion polar molecules, which are present in large quantities in all food products. As a result of the intense movement of molecules, food quickly heats up.
During the operation of the microwave the temperature inside the chamber reaches very high values, therefore, the design provides for a special element that protects the device from overheating - a thermal fuse (thermal relay). The main part of the thermostat is a bimetallic plate that can change shape under the influence of temperature.
When the heating level reaches its limit values, the plate changes shape and forces a pusher to act, which opens the connection of the plates of the contact group and stops the operation of the microwave oven. As the temperature decreases, the regulator plate returns to its original position, the contacts close, the device starts its work again.
Besides household use, microwave ovens are used in industry. They are used for processing building materials, softening rocks, oil reclamation, etc.
