Ultraviolet Lights

May 21, 2024

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Table of Contents

Introduction

The electromagnetic radiations consisting of 100 nm to 400 nm of wavelength are called ultraviolet lights. The main source of ultraviolet rays is sunlight. The wavelength of the ultraviolet rays is shorter than the visible light but longer than the X- rays. Ultraviolet rays can also be produced artificially through black lights, mercury-vapour lamps, and many more.

The ultraviolet lights are invisible to the human eye. Along with this, the human eye also blocks the colour receptors of ultraviolet light. The retina of human eyes is susceptible to ultraviolet rays. The UV lights are visible to a few insects, mammals, and some birds. The word ultraviolet means beyond violet. It is named this because the highest colour frequency of visible light is violet, and ultraviolet light crosses that frequency.

Subtypes of UV Light

The ultraviolet light spectrum can be subdivided into a few ranges of wavelengths. These ranges give the subtypes of ultraviolet rays. These subtypes are provided below:

Ultraviolet A, wavelength: 315-400 nm.
Ultraviolet B, wavelength: 280-315 nm.
Ultraviolet C, wavelength: 100-280 nm.
Near ultraviolet, wavelength: 300-400 nm.
Middle ultraviolet, wavelength: 200-300 nm.
Far ultraviolet, wavelength: 122-200 nm.
Hydrogen Lyman- alpha, wavelength: 121-122 nm.
Extreme ultraviolet wavelength: 10-121 nm.
Vacuum ultraviolet, wavelength: 100-200 nm.

Artificial Sources of UV Lights

Sunlight is the natural source of ultraviolet light. However, there are several artificial sources of ultraviolet rays too. Some of these are mentioned below:

Black lights

A black light lamp emits very little visible and long-wave UV light. There are fluorescent black light lamps, almost like other fluorescent lamps. The only difference is that these fluorescent black light lamps use a phosphor on the surface of their inner tube, which is the primary source of emitting UV-A lights instead of visible light. Black light is used when there is no visible light, and its extraneous light must be minimised. Especially, The black light lamp is used to observe fluorescence given by substances.

Short Wave Ultraviolet Lamps

The fluorescent lamps made with no phosphor coating are called short-wave ultraviolet lamps. The glass of these lamps is made up of fused quartz because ordinary glass can absorb ultraviolet C lights. However, due to the mercury and visible light in these lamps, they emit a UV-C band at 185 nm and 253.7 nm wavelengths. Short-wave UV lamps are extensively used in disinfecting laboratory surfaces and the surfaces of food processing industries. They are also helpful in the disinfection of water supplies.

Incandescent Lamps

Incandescent lamps are electric light lamps along with a wire filament that remains heated till it is glowing. The filter coating applied on the black light Incandescent lamps is capable of absorbing visible light. Halogen lamps, and fused quartz, are used in making these Incandescent lamps as they are inexpensive UV light sources.

Ultraviolet LEDs

LEDs, also known as Light Emitting Diodes, are manufactured to emit UV light radiations. These LEDs are used in digital print applications, curing applications, inerting UV curing environments, and many more. The most common type of LEDs, including UV lights, are of 365 nm and 395 nm wavelength, emitting UV-A spectrum.

Applications of UV Lights

Ultraviolet lights are considered to have numerous applications based on their ability to cause chemical reactions. Some of its applications are provided below:

Photography

The photographic films only respond to ultraviolet light photography, reflected by UV lights, and are extremely useful in medical, scientific, and forensic research and investigations. UV lights are crucial for detecting burns on the skin, altering a document, and many more.

Chemistry

In the chemistry field, UV lights play a crucial role. To analyse chemical structures, UV spectroscopy is used. For detecting CECs in water samples, UV radiations are used in environmental chemistry. In addition, UV lights are used to excite fluorescent emissions, which are measured in a spectrofluorometer.

Air Purification

The UV lights reduce gaseous containment in the environment, such as carbon monoxide and Volatile organic compounds. UV lamps which radiate at the wavelength of 184 nm and 254 nm, can remove low concentrations of toxic gases like carbon monoxide. This method is also helpful in preventing the ozone layer from getting into contact with the treated air.