Infrared ray, also often called infrared radiation, is a kind of "invisible light". Infrared rays are widely used, and the following applications are common:
In the infrared region, the band of 4 ~ 14 micron is most beneficial to human body and has magical energy for the growth of life in the universe. The survival and reproduction of all animals and plants are carried out under the infrared light with a specific wavelength, so many experts and scholars call it "fertility light". Far-infrared textile is a new type of precision ceramic powder made by special processing in recent years, which has the functions of activating tissue cells, promoting blood circulation and improving microcirculation, enhancing immunity, enhancing metabolism, diminishing inflammation, deodorizing, relieving itching and inhibiting bacteria.
Many household appliances in daily life are inseparable from the remote control. Many household appliances are equipped with infrared remote control devices. The remote controller and the infrared receiver are in a straight line, and the best effect is achieved when the left-right deviation does not exceed 15.
Nowadays, more and more electronic devices are equipped with infrared ports, which support wireless transmission and avoid the tedious connection through cables. If you use infrared rays, you can surf the Internet through your mobile phone.
Using infrared rays can also prevent theft. It consists of an infrared transmitter and an infrared receiver. The infrared beam emitted by the infrared emitter forms an invisible blockade line. When someone crosses or blocks the infrared ray, the receiver will start the alarm host, and the alarm host will call the police immediately after receiving the signal.
Infrared switch. There are two kinds of infrared switches: active and passive. The active infrared switch consists of an infrared emitting tube and a receiving tube. When the receiving tube receives the infrared ray emitted by the transmitting tube, the lamp is turned off; When the human body blocks infrared rays, the light is turned on. Passive infrared switch uses human body as infrared light source (the temperature of human body is usually higher than the ambient temperature), and lights up the illuminating lamp when infrared radiation is detected.
Use infrared photography. According to the test, the infrared ray in natural light radiation can reach more than 40%. In black-and-white photography, special filters can be used to block red-crimson-dark red visible light, thus making infrared images sensitive on film. For example, the "Leiden 87C" filter can block almost all visible light and produce pure infrared photography effect, which is almost invisible to the naked eye. In specific operation, the focal length should be adjusted first, and then the filter should be added. In addition, shooting requires normal exposure. Generally speaking, "Leiden 25" red mirror can be used for infrared photography and can also produce obvious infrared effect. So what is the reason for infrared photography? The brightest objects seen by human eyes, such as blue water and sky, can't reflect more infrared light, so that although the imaging of ordinary black-and-white film is normal, the color of infrared film is dark. The reason why trees and grasslands turn pale is that chlorophyll can reflect a lot of infrared rays, thus achieving an unrealistic artistic conception. Infrared ray not only provides a special creative technique for photography, but also can take clear photos in fog and smoke due to its high transmittance. It is often used in exploration and military reconnaissance in scientific research. Using the characteristics of infrared rays penetrating the surface of the picture and pigment, we can also judge the authenticity of the famous paintings of masters.
In the dark, various mineral deposits can be detected by infrared remote sensing equipment. China investigated geothermal resources and radioactive mineral resources by using infrared remote sensing photos.
In the military field, infrared can also play an important role, such as infrared reconnaissance and infrared guidance. Reconnaissance satellites with infrared imaging equipment can get more information about ground targets, identify camouflage targets and monitor ground military operations at night. The missile early warning satellite can detect the infrared radiation of the engine tail flame when the missile is launched and give an alarm, which provides a certain early warning time for intercepting the incoming missile. Infrared guidance is to use the infrared radiation of the target itself to guide the missile to approach the target automatically, thus improving the hit rate. It is said that before Iraq attacked Kuwait, in order to prevent American planes from blowing up Iraqi chariots, many tunnels were dug in the desert and the chariots were hidden in the tunnels under the desert during the war. A piece of yellow sand rolled, making the American plane unable to find the position of the chariot. Unfortunately, the temperature in the desert is very high during the day, and the chariots are mostly metal, which absorbs a lot of heat. At night, the surface temperature of the desert drops rapidly, but the temperature of the chariot buried in the sand is higher than that of the surrounding sand (with large heat capacity), and it radiates invisible infrared rays. So American planes use infrared detectors at night to clearly see every chariot under the sand. So all the chariots were destroyed.
In recent years, infrared rays have been widely used in military, artificial satellites, industry, health and scientific research, so infrared pollution problems have also arisen. Infrared ray is a kind of thermal radiation, which will cause high temperature damage to human body. Strong infrared rays can cause skin damage, similar to scalding, burning pain first, then burning. In several different situations, infrared rays can hurt the eyes. The infrared ray with the wavelength of 7500 ~ 13000 A has a high transmittance to the cornea, which can cause damage to the fundus retina. In particular, infrared rays of about 1 1000 angstrom can make anterior media (corneal lens, etc. ) eyes are not damaged and directly cause fundus retinal burns. Almost all infrared rays with the wavelength above 19000 A are absorbed by the cornea, which will cause corneal burns (opacity and white spots). Most of the energy of infrared ray with wavelength greater than 14000 angstrom is absorbed by cornea and intraocular fluid, but it cannot penetrate iris. Only infrared rays below 13000 angstrom can penetrate the iris, causing iris damage. If human eyes are exposed to infrared rays for a long time, it may cause cataracts. Therefore, when we use infrared rays, we should also be alert to its harm.
absorption spectrum
Absorption spectrum is a curve drawn by absorption wavelength or other functions of wavelength after absorbing electromagnetic radiation. It is the result of selective absorption of light with different wavelengths by substance molecules, and it is the main basis for the study of substance spectrophotometry. The absorption spectrum is white light emitted by a high-temperature light source, which is produced by passing through low-temperature steam or gas. The frequency of light emitted by each element is the same as the frequency of light absorbed by it.