How Do UV Rays Impact Daily Life and Scientific Discoveries?
Ultraviolet (UV) light is a type of electromagnetic radiation on the electromagnetic spectrum. The frequency of UV light is higher than that of visible light. This means it has more energy, which makes its wavelength shorter. This increased energy causes chemical effects in many objects — such as skin, plastics, and even some clothing dyes.
One major difference between UV and visible light is its wavelength; UV has a smaller wavelength than visible light. The electromagnetic spectrum is divided into different “bands” depending on wavelength - ultraviolet light is the shortest, while infrared light is the longest. The term “visible light” refers to the part of the spectrum that the human eye can see.
A majority of the UV rays that humans come in contact with the sun. However, other UV light sources also exist. Black lights, mercury lamps, and tanning lights all emit at levels of UV radiation.
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Wavelength and Frequency of UV Rays
Electromagnetic waves work differently. All waves of the same type of frequency travel at the same speed. But their wavelength and frequency differ, depending on the type of wave. The frequency of a wave is measured in Hertz; its unit is Hz.
UV light wavelengths are measured in nanometres, with one nanometre equal to one billionth of a metre. Ultraviolet rays are shorter wavelengths than visible light, which is why we cannot see them when seen naked-eye.
Ultraviolet rays are in the wavelength range from 10 to 400 nanometers (nm). They come in the frequency range of 800 terahertz (THz) to 30 petahertz (PHz). Ultraviolet radiation is usually divided into four regions.
The first region is near, which goes from 400–300 nm.
The second region is in the middle, which is 300–200 nm.
The third region is far, which ranges from 200–100 nm.
The last region is extreme, which goes below 100 nm.
Types of UV Light
UV Rays are separated into three groups: UV-A, UV-B, and UV-C. Each group has a distinct characteristic.
Ultraviolet A (UVA) | Ultraviolet B (UVB): | Ultraviolet C (UVC) |
1. 98.7% of the UV light reaching Earth is UVA. It is affected by the ozone. 2. Fading of paints and dyes. 3. UVA causes early ageing of the skin. 4. UVA causes skin cancer called melanoma. | 1. 1.3% of the UV reaches the earth’s surface and is highly affected by ozone. 2. For the production of vitamin D, 270-300 nm wavelengths are responsible. | 1. UVC rays do not reach the earth’s surface as most of them are absorbed by the atmospheric nitrogen, oxygen, and ozone, and the rest are scattered. 2. UVC causes lesions on the skin. |
Use of Ultraviolet Rays
Ultraviolet light has many uses, including treating skin diseases like lupus and vitiligo, but photography is one of its most common uses. The same technology that produces blacklight posters, fluorescence art, sunless tanning solutions, and teeth whitening products also provides us with protection from pests like bed bugs. Here are some of UV light uses in detail:
UV Light in Tanning - Sunburn is a result of too much exposure to dangerous UV light. The body’s natural defence mechanism kicks in and produces a pigment called melanin. The body sends this pigment into neighbouring cells to try and prevent damage. Tanning beds use UV lights that pass electric currents through vaporised mercury to create the sun's rays.
Lamps - Lots of substances can absorb UV light. Some naturally occurring substances like plants and fungi and some man-made substances like synthetic fluorophores will do it too - one of them being fluorescent lamps. When UV light is absorbed, electrons in the material reach a higher energy level before gradually returning to their original position. Each time they do so, they release a small amount of the energy they have absorbed as visible light.
Cancer Treatment - One of the benefits of UVA light is that it can be used to treat skin cancer. Psoralens, or drugs, are given to patients to react to the UVA light and slow the growth of cells on the body. Patients who use this treatment experience great benefits, such as having treatments with lamps similar to tanning beds. There is some risk of burning the skin if not careful, but proper calibration will minimise this risk.
Chemistry - UV lights are used by scientists to examine the chemical structure of a compound. The sensitive machine, called a spectrophotometer, monitors colour changes in UV light radiation to determine how much of a certain compound is present. This process is often used in a variety of industries. For example, it can identify unwanted compounds in water by monitoring a change in colour during drinking water production.
Photography - UV photography is a specialised type of photography that allows photographers to capture images with UV light. Most UV photography is used for medical, scientific and forensic purposes. Nature photographers may take pictures of flowers with UV photography because the human eye can’t see these details. By using UV photography, they can capture only the UV light that hits the camera sensor.
FAQs on UV Rays: Definition, Properties & Applications
1. What are UV rays as explained in the electromagnetic spectrum?
Ultraviolet (UV) rays are a form of electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays. In the electromagnetic spectrum, they are located between violet light (400 nm) and X-rays (10 nm). UV radiation is invisible to the human eye but carries more energy than visible light, which allows it to cause chemical reactions and make certain substances fluoresce.
2. What are the different types of UV rays and how do they differ?
UV radiation is primarily classified into three main types based on their wavelength. Understanding these types is crucial for grasping their different effects:
- UVA (315–400 nm): This is the longest wavelength UV radiation. It can penetrate deep into the skin's layers and is primarily responsible for skin ageing and wrinkling. About 95% of the UV radiation reaching the Earth's surface is UVA.
- UVB (280–315 nm): UVB rays have a shorter wavelength and are more energetic than UVA. They are responsible for causing sunburn and play a key role in the development of skin cancer. They are also essential for the synthesis of Vitamin D in the skin.
- UVC (100–280 nm): This is the most energetic and dangerous type of UV radiation. Fortunately, it is completely absorbed by the Earth's ozone layer and atmosphere, so it does not reach the ground.
3. What are the most common natural and artificial sources of UV rays?
UV rays are produced by various sources, both natural and man-made. The most significant sources include:
- The Sun: The primary natural source, emitting a continuous spectrum of UVA, UVB, and UVC rays.
- Artificial Sources: These include tanning beds, which primarily use UVA lamps; mercury-vapour lamps used in streetlights and gyms; certain halogen, fluorescent, and incandescent lights; and welding arcs, which produce intense UV radiation.
4. What are the key industrial and medical applications of UV radiation?
Despite their risks, UV rays have several important applications. Their ability to kill microbes and cause chemical reactions is harnessed in various fields:
- Sterilisation and Disinfection: UVC lamps are widely used to sterilise surgical equipment, purify drinking water, and disinfect air in hospitals, as they effectively destroy bacteria and viruses.
- Medical Therapy: UV light is used in controlled doses for phototherapy to treat skin conditions like psoriasis and vitiligo.
- Curing and Printing: In manufacturing, high-intensity UV light is used to instantly cure or dry inks, coatings, and adhesives.
- Forensics: UV light can cause bodily fluids and certain substances to fluoresce, making it a valuable tool in criminal investigations.
5. How can UV rays be both beneficial and harmful to the human body?
UV radiation has a dual effect on human health. On one hand, exposure to UVB rays is the most natural way for the body to produce Vitamin D, which is essential for bone health and immune function. On the other hand, overexposure can be very harmful. It can lead to painful sunburn, premature skin ageing (photoageing), eye damage like cataracts, and significantly increases the risk of developing skin cancer, including melanoma.
6. How does the Earth's ozone layer specifically protect us from solar UV radiation?
The ozone layer in the Earth's stratosphere acts as a critical protective shield against solar UV radiation. When UV rays from the sun travel towards Earth, the ozone (O₃) molecules absorb them. This process is most effective for the shortest, most energetic wavelengths. The ozone layer completely blocks all UVC radiation and absorbs about 95% of the UVB radiation. It allows most of the UVA radiation to pass through, which is why we still experience the effects of UVA on the ground.
7. Can you still get a sunburn on a cloudy day? Why or why not?
Yes, you can definitely get a sunburn on a cloudy day. This is a common misconception. While heavy, dense clouds can block a significant portion of UV rays, thin or scattered clouds may not. Clouds block more visible light than UV radiation. Up to 80% of the sun's UV rays, particularly UVA, can penetrate through light cloud cover and haze, reaching your skin and causing damage. Therefore, sun protection is necessary even on overcast days.
8. Why is UV radiation considered more energetic than visible light?
The energy of an electromagnetic wave is directly proportional to its frequency and inversely proportional to its wavelength, as described by the equation E = hf (where E is energy, h is Planck's constant, and f is frequency). UV rays have a higher frequency and shorter wavelength than visible light. This higher frequency means each photon of UV light carries more energy than a photon of visible light, giving it enough power to break chemical bonds in molecules, including those in our skin and DNA.
