Ultraviolet Frequency ratio Visible light is higher, but lower than X-ray. The range wavelength of ultraviolet light in electromagnetic spectrum is 400-10nm. This range starts from the high frequency limit of visible light and overlaps with the low frequency of X-ray. Ultraviolet light is divided into A ray, B ray and C ray (respectively referred to as UVA 、 UVB And UVC), Wavelength range They are 400-315nm, 315-280nm and 280-190nm respectively. Function 1: sterilization
This is ultraviolet rays The most common features of. Since ultraviolet rays have a strong killing power on living things, human beings use them to deal with these troublesome bacteria Viruses People often use sunlight to kill bacteria. However, it should be noted that these Sterilization equipment It will also hurt the human body, so you should be very careful when using it. Function 2: identification and perspective
Because ultraviolet light has more penetrating ability than ordinary visible light, scientists often use ultraviolet light to carry out perspective or identification work (just like using X-ray health examination Same). For example, using ultraviolet light to check the authenticity of pictures Food Safety , even when exploring space, ultraviolet light can be used. Function 3: health and medical treatment
Excessive ultraviolet exposure will cause harm to human body (such as skin cancer), but proper sunshine can help human body to synthesize vitamin D 。 Recently, it has been found in medicine that a moderate amount of A or B light can treat psoriasis Leukoplakia Such as skin lesions, so that patients no longer "itchy". However, this "light treatment" can only be carried out under the guidance of doctors, because excessive radiation may cause side effects or permanent damage to some people's bodies. Function 4: insect Guide the way Because each kind of creature can receive light with different frequency ranges, some animals have to rely on ultraviolet light to find their way or see objects clearly. For example, when bees look for nectar and pollinate flowers, they also need to use ultraviolet light. In addition, ultraviolet radiation is also carried out by plants photosynthesis An indispensable raw material of. 
