What Is The Difference Between UVA, UVB, And UVC?

Published Date: 2023-02-23 14:33:19 Views: 277

What is UV?

Ultraviolet (UV) is the name given to the electromagnetic waves emitted by the sun at wavelengths between 100 and 400 nm, which are invisible to the human eye. Ultraviolet light is usually divided into three types according to its wavelength: near ultraviolet (UVA), far ultraviolet (UVB), and ultra-short ultraviolet (UVC), of which UVC is very energetic and destructive to microorganisms, but when it passes through the stratosphere at the Earth’s surface it is essentially absorbed by the ozone layer and cannot reach the Earth’s surface.

UV spectrum

Differences between UVA, UVB, and UVC

The following are all three measured wavelengths in nm:

  • UVA: 420-320nm
  • UVB: 320-280nm
  • UVC: 100-280nm (Germicidal UVC available)

Damage to the skin

UV rays can be very harmful to the skin. Prolonged exposure to UVB rays can damage the skin. Because UVA, UVB, and UVC have different wavelengths, they have different effects on the skin.

The shorter the wavelength of ultraviolet light, the greater the radiation hazard, but the less the radiation penetrates the skin.


UVA has the longest wavelength between 320-400nm. It can penetrate clouds, and glass in rooms and cars, and shoot into the dermis of the skin, causing sunburn and redness, and is the main cause of skin aging and wrinkles.


The wavelength range of ultraviolet B rays is 280-320 nanometres, and a very small percentage of UVB can pass through the atmosphere to reach the earth’s surface.

These rays can reach the surface of the skin but cannot penetrate the inner layers. Scientific studies have shown that UVB can also cause skin diseases, which can lead to redness, swelling, and heat pain, and that UVB is highly carcinogenic.


The wavelength of UV-C is between 100-280nm, the shortest of all wavelengths. UV-C is blocked by the ozone layer and does not reach the earth’s surface, causing less damage to human skin. In addition, all available UV-C comes from artificial light sources.

Advantages of UVC sterilization

Broad-spectrum sterilization: UV sterilization has a high degree of penetration and can destroy almost all microorganisms, including bacteria, tuberculosis, viruses, spores, and fungi.

High efficiency: UVC disinfection is fast and effective. At a certain radiation intensity, common pathogenic microorganisms can be killed in just over ten seconds, as well as some bacteria that cannot be inactivated by chlorine disinfection.

Environmental protection: Germicidal UVC does not require the addition of chemicals. It kills bacteria directly or destroys their ability to reproduce by short-wave radiation, leaving no contamination or residue and no secondary pollution of the environment.