Infrared and Ultraviolet Light
Infrared light is a form of electromagnetic radiation whose wavelengths are longer compared to visible light. The electromagnetic spectrum exhibits a vast range of wavelengths spanning from highly energetic gamma rays and short wavelengths to low-energy radio waves and long wavelengths. The visibility of this spectrum is extremely small. Infrared light is similar to normal light only that it has a longer wavelength thus making it impossible to see with the naked eye (White 42). The range of infrared wavelengths corresponds to an approximate frequency range of 430 THz to 300GHz. It also includes the thermal radiation given off by objects at room temperature. Infrared light is absorbed or emitted by molecules whenever they alter their vibrational-rotational movements.
William Herschel discovered infrared radiation in the year 1800. He was performing a study on the heating effect of different light colors. The different colors of light were produced by a passing normal light through a prism. In his study, Herschel noted that the strength of the heat increased as he progressed from the blue end to the red end of the spectrum. He presented his results in London and called the red light ‘Calorific rays’. The term ‘infrared’ was adopted later in the 19th century (Read 32).
Primarily, infrared is divided into three distinct spectrums. These include far infrared, mid infrared and near infrared. The division of infrared light on this basis depends on the wavelength. However, these divisions are not precise since they vary depending on the publisher. These divisions are used to observe temperature ranges in environments such as space. They are justified by the different responses humans have on radiation. In this case, near infrared exhibits radiation with the closest wavelength. This makes it visible to the human eye. Far and mid infrared categories, lie further away from the visual spectrum. Unfortunately, there are no international standards for such specifications. The boundary separating infrared light from visible light is not defined clearly. The sensitivity of the human eye is not designed to detect light with a wavelength above 700nm (White 64). Therefore, light with longer wavelengths does not make significant contributions to scenarios illuminated by common sources of light.
Since its discovery, infrared light has proven useful in a number of fields. For example, infrared is used to facilitate night vision. Night vision devices function by converting ambient light photons into visible light. Additionally, infrared light can also be used in determining the temperature of objects through a process known as thermography. Thermography is mainly applied in industrial and military applications (Read 64). However, this technology is making its way into the public through infrared cameras, due to the reduced cost of productions. Since all objects emit infrared radiation based on their temperatures, thermography is used to have a clear picture of the environment regardless of whether there is visible illumination or not.
Infrared homing or infrared tracking refers to a missile guiding system that tracks a target using its electromagnetic spectrum. Missiles that use this infrared technology are coined the term ‘heat seekers’. Many objects such as vehicle engines, aircrafts and people produce and retain heat. This heat can then be tracked using infrared technology. Additionally, infrared radiation can be used as a source of heat. One advantage of this is that the technology is used to create infrared saunas used to treat chronic health illnesses such as arthritis, congestive heart failure and high blood pressure. This technology is also used to thaw ice on aircraft wings. Infrared radiation is also becoming popular in safe heating therapy for physiotherapy and natural health. Additionally, heat from infrared radiation can be used in cooking. Primarily, infrared heaters include three parts, a heat exchanger, infrared bulbs, and a fan for blowing air into the exchanger for heat dispersion.
Indeed, the discovery of infrared radiation has led to significant breakthroughs that have benefited humanity. However, this form of electromagnetic radiation has several disadvantages. For example, when this radiation is used in certain settings such as high heat industrial locations, it becomes a health hazard to the user’s eyes thus causing damage or blindness. Another disadvantage is that it has short-range transmission compared to other forms of transmission. Other than having short-range transmission, the transmission of infrared radiation is slow compared to wired transmission. Furthermore, all infrared signals can be interrupted by foreign materials when they are in the path of the transmission. Such materials may include people and walls.
Ultraviolet light or UV light is a form of electromagnetic radiation with a short wavelength compared to visible light. However, its wavelength is longer than that of X-rays. Similar to infrared light, ultraviolet light cannot be detected by the human eye due to its long wavelength. Blunt (18) argues that this form of radiation bears increased energy compared to visible light. It is capable of breaking bonds between molecules and atoms and altering the chemical composition of materials. UV light can also cause fluorescence in certain substances. This means that it causes certain materials to emit visible light. UV light, present in sunlight, is beneficial since it kills microorganisms and acts as a source of vitamin D.
Even though UV light is not visible, we are aware of it through certain effects such as sunburn or suntan. With the sun acting as a major source of UV light, the ozone layer plays a vital role in blocking most of this light (97%) that would otherwise prove harmful to organisms if it gained access into the atmosphere (Blunt 37). The 3% that penetrates the atmosphere is not particularly harmful, although it can cause cancer and long-term damage to the skin. Primarily, the sun is a source of all categories of UV light such as UV-A and UV-B.
The discovery of this radiation is associated with the phenomenon that silver salts become dark when exposed to light. Johann Ritter in 1801 observed that invisible light, after the violet end of visible light, darkened paper soaked in silver chloride. Initially, he named these rays “oxidizing rays” to differentiate them from heat rays (infrared) discovered in the previous year and to emphasize chemical reactivity. The terms “heat rays” and “chemical rays” were used to describe these rays throughout the nineteenth century, but they were later dropped for infrared radiation and ultraviolet radiation respectively (Read 32).
UV light, UV-B in particular, benefits humans by allowing the manufacture of vitamin D. This is achieved by the conversion of skin chemicals into the sub-form of the vitamin, and then into the vitamin itself. This vitamin is beneficial to human health. Lack of this vitamin leads to immunity disorders, various cancers, high blood pressure, and cardiovascular diseases (Blunt 76). Severe lack of this vitamin causes bone diseases referred to as rickets. Inadequate supply of sunlight is the prime cause of the vitamin’s deficiency.
UV light is also used in the technology of fluorescent lamps that apply the fluorescence phenomenon (Read 81). Most fluorescent lamps use UV light as their energy source to ionize mercury vapor. A special fluorescent coating absorbs this ionized vapor to produce visible light. Zoologists and biologists use ultraviolet light to take night surveys on organisms in the field. UV light is also used as insect traps. Since insects are naturally attracted to UV light, entomologists use it to attract them for studies. UV fluorescence is also used in parties and nightclubs by causing clothing to glow and make it appealing.
Astronomers also use UV light in mapping galaxies such as the Milky Way. This allows them to make out the evolution of galaxies over time. Primarily, young stars emit more ultraviolet radiation compared to older stars. They also emit UV light at a higher proportion at the furthest end of the spectrum. Regions where new stars are born, therefore, produce a brighter UV glow. Astronomers use this knowledge to identify and map such regions. Despite the numerous benefits UV radiation provides humanity, it also has disadvantages. The ability of UV light to change the chemical composition is harmful. As UV light causes minor skin irritations such as sunburn, radiation that is more energetic, can lead to premature skin aging (Blunt 97). It can also lead to alterations of the DNA that can eventually cause skin cancer. Furthermore, overexposure to ultraviolet light causes the skin to produce a pigment known as melanin. Melanin is harmful to the skin and can lead to cancers such as melanoma.
Blunt, Katharine. Ultraviolet Light. Chicago, Ill: The University of Chicago press, 2011. Print.
Read, F H. Electromagnetic Radiation. Chichester [Eng.: J. Wiley, 2010. Print.
White, Laurie. Infrared Radiation. Amherst, N.Y: Amherst Media, 2009. Print.