What is the Differences Between UV-A and UV-C?

The variety of hues in the visible spectrum is about equal to that of ultraviolet light. However, we often overlook this when considering UV light, only classifying it as a spectrum of wavelengths linked to its possible cancerous effects as well as its utility in fluorescence, curing, and disinfection. However, because each type of ultraviolet energy has highly diverse qualities, it is crucial to distinguish between them. The main distinctions between UV-A and UV-C radiation in terms of their usage and applications are covered in this article.

The primary way to identify ultraviolet energy is by its wavelength. The type of ultraviolet energy is determined by the wavelength value, which is expressed in nanometers (nm). Wavelengths between 315 and 400 nanometers are included in UV-A, and those between 100 and 280 nanometers are included in UV-C. The wavelengths of UV-B range from 280 to 315 nanometers.

In the same way that humans cannot visually determine if a light source is red or blue, it can be somewhat counterintuitive to know that UV-A and UV-C are both invisible to the unaided eye. Knowing what wavelength light source you will require for your specific application-or at the very least, understanding the distinctions between UV-A and UV-C radiation-is therefore even more crucial.

The majority of UV-A lamp applications use a wavelength of 365 nanometers and can be classified as either fluorescence or curing applications. The process by which substances like paints, pigments, or minerals transform UV-A energy into a visible wavelength is known as fluorescence. 365nm curing UV lamps used for these purposes are known as blacklights because, although they appear dark, they emit a variety of visible colors when shone on different objects.

An illustration of a rock exhibiting green fluorescence under the realUVTM LED flashlight may be found below. In many fields, including forensics, medicine, molecular biology, and geology, UV-A fluorescence is particularly useful because it may be used to detect the presence of fluorescent materials that would otherwise be impossible to discriminate under normal illumination conditions.
Applications of fluorescence are not limited to the scientific domain. Fluorescence can be utilized for blacklight art installations and fluorescence photography, among other amazing visual effects. You may or may not recall that blacklight party, but many other entertainment venues will also employ UV-A to produce fluorescence effects.
365 nm and 395 nm are the most often observed wavelengths for UV-A fluorescence. Both 395 and 365 nm will typically produce fluorescence effects, although 395 nm will have a slight visible violet/purple component, while 365 nm will provide a "cleaner" UV effect with less visible light output. See our article comparing 365 nm and 395 nm for additional details.

In contrast to fluorescence, UV-A is utilized in curing applications and has the ability to cause chemical and structural alterations in a variety of materials. Curing is often achieved with the same UV-A wavelengths but necessitates a much higher degree of UV intensity. Similar to fluorescence, 365 nm is a frequently utilized curing wavelength.

UV-A radiation is used to cure emulsion paint in screen printing, as well as to cure industrial epoxies and nail gels. For UV-A curing applications, exposure duration is just as important as intensity.

UV-C wavelengths are substantially smaller, ranging from 100 nm to 280 nm, than UV-A wavelengths. Pathogens such as bacteria, molds, fungus, and viruses can be effectively rendered inactive by using UV-C wavelengths.

Since DNA and RNA can be damaged at and around 265 nanometers, UV-C is an effective germicidal wavelength. Through a process known as dimerization, double bonds holding thymine and adenine together are broken when pathogens are exposed to UV-C wavelength light, changing the genome's structure. Because of this change, the virus is unable to successfully replicate or multiply when it tries to do so because of the genetic corruption.

Because thymine (uracil in RNA) is wavelength sensitive, UV-C has a special capacity to carry out germicidal actions. According to the chart below, uracil and thymine are incapable of absorbing UV light at wavelengths longer than 300 nanometers.
The graphic illustrates that UV-C radiation has the capacity to start dimerization, whereas UV-A radiation does not. Because UV-A cannot target the DNA structures of pathogens, it is not an effective disinfection approach, according to all available information.

It's a frequent misperception that natural daylight contains UV rays of all kinds. All UV energy wavelengths are included in solar radiation, however only UV-A and certain UV-B rays can penetrate the earth's atmosphere. In contrast, UV-C does not reach the ground because it is absorbed by the ozone layer.

All ultraviolet energy must be handled with extreme caution since, according to the US HHS, all UV wavelengths-including UV-A, UV-B, and UV-C-are thought to be carcinogenic. Since UV radiation is invisible, it can be particularly harmful since, unlike visible light, it does not cause the body to naturally squint or turn away. There are, however, a lot more research and population-level studies that provide us some insight of the possible hazards and harm that UV-A might bring because we do know that UV-A radiation is rather common during natural daylight.

On the other hand, the average human does not regularly come into contact with UV-C radiation. For particular sectors and professions, like welding, the majority of studies have been conducted with occupational health and safety in mind. Consequently, far less research has been done on the dangers and possible damage posed by UV-C. Because of its shorter wavelength, UV-C has a significantly higher energy level from a physics standpoint, and we know that it directly destroys DNA molecules. It would be wise to presume that it could be more harmful to humans than UV-A and UV-B, which are weaker types of UV. Therefore, much greater care should be taken to prevent UV-C exposure.