What Are UV Rays?
The term UV light or UV rays has been a familiar term for us. Here we will get to know the details of this term. What is UV light or what are UV rays? The full form of UV in UV rays is ultraviolet. Ultraviolet means "beyond violet". In visible light, the color violet has the highest frequency. Ultraviolet has a higher frequency (and thus a shorter wavelength) than violet light. Its wavelength ranges from 10nm to 400nm. The corresponding frequencies are approximately 30 PHz to 750 THz. Its wavelength is shorter than that of visible light but longer than X-rays. Sunlight contains UV light and constitutes around 10% of the total electromagnetic radiation output from the sun. In 1801 a German physicist Johann Wilhelm Ritter discovered UV radiation.
Ultraviolet radiation is basically a type of electromagnetic radiation. These rays are a part of energy coming from the sun. These rays are quite harmful to us but are stopped by the earth's ozone layer from entering the earth's atmosphere. These rays are invisible to most of the humans as the human eye lens blocks the rays of wavelengths ranging from 300nm to 400nm and the shorter wavelengths are blocked by the 'cornea' of the eye. Also, we lack colour receptor adaptation for UV rays. However, some children or young adults might be able to these rays of lower wavelength. Also, some insects and mammals can see these radiations. Electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights also produce it.
Types of UV Rays
The UV ray spectrum is broadly classified into three major divisions. However, there are some other subdivisions as well. We can see the divisions in the table given below.
Other Subdivisions Are
Suitable photodiodes and photocathodes can detect ultraviolet. These are sensitive to different parts of the UV spectrum. Sensitive ultraviolet photomultipliers are also used. The measurement of UV radiation is done by spectrometers and radiometers. Silicon detectors are also used across the spectrum.
UVA is the type that reaches the most to us on earth's surface hence not affected by ozone.
It is a black light and called soft UV.
Since it reaches us hence can cause skin cancer called melanoma.
UVB is highly affected by ozone as only 1.3% of it reaches the earth's surface.
It is responsible for tan and skin burns.
It is called intermediate UV.
It is stimulated for the production of vitamin D.
UVC is completely absorbed by ozone and atmosphere and most of it is scattered.
It is hard UV.
It causes lesions on the skin.
H Lyman-α is ionizing radiation at shorter wavelengths.
The specific wavelength of VUV can propagate through nitrogen but most of it is strongly absorbed by atmospheric oxygen.
EUV is completely absorbed by the atmosphere and is strong ionising radiation.
What is UV Light Used For?
UV light has the ability to cause chemical reactions and excite fluorescence in materials, so it has a wide range of applications.
UV is useful in photography using different filters and different lenses for different wavelengths. Some cameras are also designed for use in UV. Medical, scientific, and forensic investigations use photography by reflected ultraviolet radiation in applications as widespread as detecting bruising of the skin, alterations of documents, or restoration work on paintings.
UV light has important uses in the electrical and electronics industry. On an electrical apparatus, corona discharge is detected by its ultraviolet emissions. Erasable programmable read-only memory (EPROMS) is erased on exposure to this light.
UV light also finds its use in fluorescent dyes. Optical brighteners to papers and fabrics are colourless fluorescent dyes emitting blue light under UV. Glowing UV fluorescent dyes are used in textiles, paints, papers, and other art and aesthetic applications.
Irrespective of the structure or colour of the surface the bodily fluid is deposited upon UV is helpful in locating and identifying bodily fluids as blood, semen, saliva. Hence, it finds an important role in crime scenes and helps in tests performed at forensic laboratories.
UV light is widely used in sterilization and disinfection. In medical and biological laboratories, UV lamps are used to sterilize the work area. UV radiation is used for disinfection in waste-water treatment.
UV radiation is used in the therapy of some skin conditions as psoriasis and vitiligo.
FAQs on UV Light
1. What is UV light and where is it found on the electromagnetic spectrum?
Ultraviolet (UV) light is a form of electromagnetic radiation with a wavelength shorter than that of visible light but longer than X-rays. Its name translates to "beyond violet," as violet light has the shortest wavelength visible to the human eye. In the electromagnetic spectrum, UV light is situated between visible light and X-rays, with a wavelength ranging from approximately 10 nm to 400 nm. The Sun is the primary natural source of UV radiation.
2. What are the main types of UV radiation and how do they differ?
UV radiation is broadly classified into three main types based on its wavelength. The key difference lies in their ability to penetrate the Earth's ozone layer and their effects on living organisms. The types are:
- UVA (315–400 nm): This is long-wave UV, often called 'black light.' It is not significantly absorbed by the ozone layer and can penetrate deep into the skin, causing premature ageing.
- UVB (280–315 nm): This is medium-wave UV. Most of it is absorbed by the ozone layer, but the portion that reaches Earth is responsible for sunburn and stimulates Vitamin D production.
- UVC (100–280 nm): This is short-wave, or 'germicidal,' UV. It is the most harmful type but is completely absorbed by the atmosphere and ozone layer, so it does not naturally reach the Earth's surface.
3. How does UV light affect the human body, both positively and negatively?
UV light has a dual impact on human health. On the positive side, exposure to UVB radiation is crucial for the body's synthesis of Vitamin D, which is essential for bone health. On the negative side, overexposure is dangerous. UVB causes painful sunburn, while both UVA and UVB can damage DNA in skin cells, leading to premature ageing and increasing the risk of skin cancer. UV radiation can also harm the eyes, contributing to conditions like cataracts.
4. What are some important real-world applications and examples of UV light?
UV light has several important applications across different fields. Some key examples include:
- Sterilisation and Disinfection: UVC lamps are highly effective at killing bacteria and viruses, making them essential for purifying water, air, and sterilising medical equipment.
- Forensic Science: Investigators use UV light to detect and identify bodily fluids like blood and saliva at crime scenes, as these substances fluoresce under UV radiation.
- Industry and Electronics: It is used for curing inks and resins, erasing data from EPROM chips, and in non-destructive testing of materials.
- Medical Treatment: In controlled doses, UV light is used in phototherapy to treat skin conditions such as psoriasis and vitiligo.
5. Why is the ozone layer so crucial for protecting life on Earth from UV radiation?
The ozone layer in Earth's stratosphere acts as a vital protective filter. It is particularly effective at absorbing the most dangerous forms of ultraviolet light. It blocks nearly 100% of the highly destructive UVC radiation and most of the UVB radiation. Without this shield, this high-energy radiation would reach the Earth's surface, causing catastrophic damage to the DNA of plants, animals, and humans, thereby making life as we know it unsustainable.
6. How can we distinguish between the biological impacts of UVA and UVB radiation?
While both are forms of UV radiation, their biological effects differ mainly due to their energy levels and depth of skin penetration. UVA has a longer wavelength and penetrates deeper into the skin, primarily causing long-term damage like wrinkles and premature ageing. In contrast, UVB has a shorter wavelength with higher energy that affects the skin's top layers. It is the main cause of sunburn and directly damages cellular DNA, which is why it is also the primary stimulant for Vitamin D production.
7. Beyond simple sterilisation, what is the scientific principle behind using UV light in forensic science?
The use of UV light in forensics is based on the scientific principle of fluorescence. Many biological fluids, such as semen, saliva, and urine, contain organic molecules that are naturally fluorescent. When these substances are exposed to high-energy, short-wavelength UV light, they absorb this energy and re-emit it at a longer, lower-energy wavelength that falls within the visible light spectrum. This process makes them appear to glow, allowing investigators to locate and identify trace evidence that is invisible to the naked eye.
