What are Ultraviolet Rays: Definition, Characteristics, Categories, Effects and Uses

Ultraviolet rays are a type of electromagnetic radiation produced by the sun that have a wavelength shorter than visible light. Despite being invisible to the human eye they can be captured by camera or other devices. These rays have many significant uses in the field of science, medicine and research. Let’s learn more about these ultraviolet rays, their characteristics, classification and uses.

Table of Contents

• What are Ultraviolet Rays
• Characteristics of Ultraviolet Rays
• Categories of Ultraviolet Rays
• Uses of Ultraviolet Rays

What are Ultraviolet Rays

Ultraviolet rays are electromagnetic waves generated by the sun and other sources that have a wavelength ranging from 100 nm to 400nm. These waves fall somewhere between visible light and X-rays in the spectrum. Along with the natural source that emits these rays, there are some artificial sources that emit them. Some of these artificial sources include UV LEDs and tanning devices.

Characteristics of Ultraviolet Rays

These radiations carry high energy and cause various chemical effects. Some key properties of ultraviolet rays include their wavelength, frequency, speed and penetration power.

• Wavelength: Spanning between the range of 100 nm to 400 nanometer, these waves are invisible to human eyes. They can cause skin aging and wrinkles.
• Frequency: Falling between visible light and X-rays, the UV rays have a frequency ranging from 8 x 1014 Hz to 3 x 1016 Hz.
• Speed: They travel at the speed of light which is 3 x 108 m/s in a vacuum. When passing through mediums like water, air or glass they travel a bit slower than in space.
• Penetration: These waves can penetrate through air and some other mediums like glass. Rays with less wavelength are less penetrating but they have higher energy.
• Ionising: UV rays can ionise atoms at shorter wavelengths.

Categories of Ultraviolet Rays 

Based on different characteristics such as wavelength, penetration and other properties UV rays are classified broadly into three main categories.

• UVA Rays: Cause sunburn and skin damage by getting deep into the skin as they have the highest wavelength from 315 nm to 400 nm. They make up the major part of the ultraviolet rays that reach the surface of the earth. 
• UVB Rays: These types of rays are more energetic than UVA rays and can get partially absorbed by the ozone layer. They have a wavelength between 280 nm to 315 nm.
• UVC Rays: Although they have the shortest wavelength they are the high energy waves among UV rays that get completely absorbed by the Earth's atmosphere under natural conditions. They are also extremely efficient in destroying bacteria, viruses and other microorganisms.

Uses of Ultraviolet Rays

• Medical Treatments: UV rays have wide applications in science and medicine. They are used in controlled manner to cure some skin diseases like psoriasis, eczema and vitiligo. These rays are also used in sterilization techniques and are also employed to disinfect medical instruments and hospital environments.
• Water and Air Purification: UVC radiation is highly efficient in damaging microorganisms such as bacteria and viruses by destroying their DNA and RNA. Due to this property of UVC rays there are UV-based purification systems used for treating drinking water, wastewater and indoor air. They help in reducing the spread of infectious diseases.
• Scientific Research: Various researchers use ultraviolet radiation for analysing molecular structures and observing astronomical events. UV rays are also helpful for studying chemical reactions, biological processes and the composition of distant celestial bodies.