What is ultraviolet light and what is it used for?

Light consists of electromagnetic waves. Some wavelengths are visible to humans, while others are not. Ultraviolet light is in the second group. We will investigate this physical phenomenon a little more.

What is ultraviolet light?

From a scientific point of view, ultraviolet light is radiation that has been given the name of ultraviolet or UV radiation. Its distinctive feature, as we have already mentioned, is its wavelength, which is between 100 nm (100 × 10−9 m) and 400 nm (400 × 10−9 m) approximately.

It was discovered by German physicist Johann Wilhelm Ritter in the early 19th century and he found out that radiation beyond the visible spectrum darkened silver chloride. Its name is due to the fact that its range of wavelength starts at the exact point in the spectrum where the human eye identifies violet light, that is, we are talking about the range beyond violet, which is imperceptible to the human eye.

The term "ultraviolet light" is very popular today, it probably sounds familiar because its rays are an integral part of sunlight. The best known are UV-A and UV-B rays. The effects produced by UV-A rays include the premature ageing of the skin, while it is UV-B rays that make your skin go nice and brown or cause what we call sunburn.

But not all the effects are negative, some of them are beneficial: They help the body to produce vitamin D which is essential for our body.

There is another type of ultraviolet rays called UV-C, which are absorbed by the atmosphere. But these types of rays can be produced artificially for applications such as medical treatments.

Is black light the same as ultraviolet light?

We have spoken about the different types of ultraviolet radiation, and these include UV-A rays and this is commonly known as ultraviolet light, although as we explained above, ultraviolet light consists of 3 different types of radiation. This light has numerous applications, and it is also known as black light or Wood's lamp.

Technology has made it possible to reproduce this long wave by using a single phosphor and a dark crystal known as Wood's crystal. This crystal filters visible light beyond the wavelength of ultraviolet rays, which is why its effects (both positive and negative) are reduced.

What is ultraviolet light for?

Because of their properties, black light or UV-A ultraviolet light lamps are used to highlight colours and effects not perceptible to the naked eye. There has been research into ways of using it, above all in the field of health.

What is it used for?

Here are some of the applications of ultraviolet light:

UV-A radiation:

• It has a therapeutic function in the treatment of jaundice in newly born children, since it breaks down bilirubin that some babies have difficulty eliminating.
• It is also used for aesthetic and recreational purposes in nightclubs and leisure venues to highlight colours, it is now very often used in the world of contemporary art.
• It is also used in the detection of counterfeit banknotes, by highlighting a hidden mark that can only be found in real banknotes.
• It is used in police investigations to locate stains and footprints at crime scenes.

UV-B radiation:

• UV-B rays are used in a similar way to UV-A rays in medicine for the treatment of skin conditions such as psoriasis, vitiligo and tumours.

UV-C radiation:

• UV-C rays have germicidal properties. They are used to purify water against chlorine-resistant bacteria.

How can homemade ultraviolet light be obtained?

It is not difficult to create homemade black light or ultraviolet light, all you need are the following materials:

• A mobile phone with a LED flash or a LED torch.
• A dark blue marker pen.
• Cello tape.

Cover your camera's flash with a piece of cello tape and paint it blue with your marker pen. Stick on another piece of cello tape and paint it blue again. Repeat the operation until there are five pieces of blue-painted cello tape covering your camera's flash. If you are using a torch, the process is the same. Turn on your LED flash or torch and what you have is ultraviolet light. Turn off the lights in your room and shine it on a brightly coloured object to appreciate the effect.