UV and IR

8 Key excerpts on "UV and IR"

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  Harmful Natural Chemicals and Radiation in the Environment

  Stories, History and What You Need to Know

  • Raymond Poon(Author)
  • 2012(Publication Date)
  • WSPC

    (Publisher)

  CHAPTER 13 ULTRAVIOLET RADIATION Source of Ultraviolet Radiation

  The sun is the primary source of natural ultraviolet (UV) radiation reaching the Earth. UV radiation occupies a non-ionizing region of the EM spectrum (see Fig. 1 , Chapter 11 ) and is categorized into UVA (315-400 nm), UVB (280-315 nm) and UVC (100-280 nm). The earth’s atmosphere acts as an effective UV blocker. By the time solar UV radiation reaches the surface of the earth, it is predominantly in the form of UVA with less than 5% UVB and very little UVC.

  The intensity of UV irradiation varies with the time of day, altitude, latitude and the seasons. On Earth, UV irradiation is the strongest near the equator and decreases towards the poles (Fig. 1 ). Seasonally, UV intensity is stronger in the summer than in the winter. On a daily basis, UV intensity peaks around noon time. Ultraviolet radiation is more intense at higher altitude as the radiation from the sun is less attenuated by the thinner atmosphere. Reflection also contributes significantly to UV irradiation. A grass lawn scatters 2-5% of incident UV radiation. Dry beach sand reflects about 10-25%. Fresh snow may reflect up to 85-90% of incident UV while water, in particular white foams in the sea, may reflect up to 30%. Clouds influence UV ground irradiance, through reflection, refraction, absorption and scattering, and may increase or decrease UV ground irradiance.21 A factor leading to increased UV reaching the earth is the depletion of the stratospheric ozone layera by halogen ions originated from man-made chemicals. An ozone “hole” is a dynamic region in the stratosphere over the Antarctica (Fig. 1 ) and the Arctic, where the ozone concentration is 50% or less of normal.

  2 -4

  Figure 1

  . The Global Solar UV Index. 2007. (UNEP GRID Aridal)

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  Thermal Energy

  Sources, Recovery, and Applications

  • Yatish T. Shah(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  Infrared is one of several ways to accomplish radiation heating along with ultraviolet (UV). Infrared light is not visible because it is beyond the spectrum we see. This invisible light gets absorbed by our skin, clothes, and other objects, which provides heat. In IR, an electrical current is passed through a solid resistor that in turn emits infrared radiation. Electric infrared heating systems are generally used where precise temperature control is required to heat treat surfaces, cure coatings, and dry materials, but infrared can also be used in bulk heating applications such as booster ovens. The work piece to be heated must have a reasonable absorption to infrared. This is determined and measured by the emissivity of the material and is helpful to determine which infrared spectrum is best suited: short, medium, or long wave.

  UV rays, on the other hand, deliver less heat, because they are less easily produced in the first place, especially by hot objects. For the same number of photons, UV delivers more energy than IR, but there is no natural circumstance where we have UV and IR light sources that just happen to generate the same number of photons. For the same intensity as IR, UV delivers the same amount of heat (because intensity is measured in the same units as energy).

  The most natural comparison between IR and UV is that the spectrum of a typical hot object is close to that of an ideal blackbody, and as shown in Figure 8.1 , for everyday temperatures, most of the energy is emitted in the IR.

  There are several physical laws that explain the properties of infrared radiation. The Stefan–Boltzmann law of radiation states that as the temperature of a heat source is increased, the radiant output increases to the fourth power of its temperature. The conduction and convection components increase only in direct proportion with the temperature change. In other words, as the temperature of a heat source is increased, a much greater percentage of the total energy output is converted into radiant energy.

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  Sun, Skin and Health

  • Terry Slevin(Author)
  • 2014(Publication Date)
  • CSIRO PUBLISHING

    (Publisher)

  Locations at the same latitude but at different longitudes can have different levels of solar UVR because one may be on the coast and another may be in the centre of a continent, e.g. Alice Springs and Brisbane in Australia. Alice Springs often has in excess of 300 sunny days a year whereas coastal regions can have more significant cloud cover and rainfall and therefore less sunshine and solar UVR.

  What exactly is UVR? The ABC of UVR

  Solar radiation covers the electromagnetic radiation spectrum and includes light or visible radiation in the wavelength range 400–770 nm as well as infrared and radio waves at higher wavelengths, and ultraviolet and X-rays, gamma rays and cosmic rays at lower wavelengths (see Fig. 2.1 ).

  Fig. 2.1: The spectrum of electromagnetic radiation, showing UVR between the visible and X-rays as well as where UVA, UVB and UVC fit in.

  The various wavelength ranges for the ultraviolet are UVC (200–280 nm), UVB (280–315 nm) and UVA (315–400 nm) as defined by the Commission Internationale d’Eclairage (CIE, International Committee of Illumination).

  First, the proportion of UVR in the sun’s spectrum is actually very very small. At the top of the atmosphere, UVA makes up only ∼6.8% of the total radiation from the sun and UVB makes up 1.4%, but at the Earth’s surface UVA makes up 6.5% and UVB makes up 0.04% of the total radiation from the sun.

  UVC is completely absorbed by the ozone layer and none reaches the Earth’s surface. Below 200 nm the UVR is strongly absorbed by oxygen in the air – only wavelengths above 200 nm can affect living tissue and organisms.

  UVR is strongly absorbed by human skin and tissue, generally being absorbed in the top layer of skin (∼0.1–1 mm deep), with the result that the skin and the eyes will be most at risk. The shorter the wavelength, the higher the energy of the photons and the more damage they can do to the cells and molecules of the body. Therefore all UVR (UVC, UVB and UVA) photons carry more energy and have a greater potential to break chemical bonds in human and biological tissue than visible photons. Similarly, within the UVR range the shorter-wavelength, higher-energy UVC photons are more likely to cause damage than UVB photons, which in turn are considered more hazardous than UVA photons.

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  Multisensor Data Fusion and Machine Learning for Environmental Remote Sensing

  • Ni-Bin Chang, Kaixu Bai(Authors)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  Identified by Einstein in 1905, quanta—or photons—stand for the energy packets that are particles of pure energy; such particles have no mass when they are at rest. While the German physicist Max Planck was developing the blackbody radiation law, he realized that the incorporation of the supposition that electromagnetic energy could be emitted only in “quantized” form was the key to smoothly interpreting the electromagnetic wave. This scientific discovery is the reason he was awarded the Nobel Prize in Physics in 1918. On the other hand, light must consist of bullet-like tiny particles, now known as photons, as Einstein pointed out in 1905. The photoelectric effect brought up by Einstein in 1905 successfully supplemented the quantization supposition that Planck proposed. This is also the reason Einstein was awarded the 1921 Nobel Prize in Physics. When possessing a certain quantity of energy, a photon is said to be quantized by that quantity of energy. Therefore, the well-known “wave-particle” duality entails the findings of Planck and Einstein that all forms of electromagnetic radiation (EMR) and light behave as waves and particles simultaneously in quantum mechanics. These findings imply that every quantic entity or elementary particle exhibits the properties of waves and particles, from which the properties of light may be characterized. Photons as quanta thus show a wide range of discrete energies, forming a basis for the spectrum of EMR. Quanta may travel in the form of electromagnetic waves, which provide remote sensing a classical basis for data collection.

  Sunlight refers to the portion of the EMR spectrum given off by the sun, particularly in the range of infrared, visible, and ultraviolet light. On Earth, before the sunlight can reach ground level, sunlight is filtered by the atmosphere. The interactions among solar radiation, atmospheric scattering and reflections, and terrestrial absorption and emission play a key role in the ecosystem conditions at the surface of Earth. Atmospheric radiative transfer processes with the effect of transmission, absorption, reflection, and scattering have collectively affected the energy budget of the atmospheric system on Earth. For example, absorption by several gas-phase species in the atmosphere (e.g., water vapor, carbon dioxide, or methane) defines the so-called greenhouse effect and determines the general behavior of the atmosphere, which results in a surface temperature higher than zero degrees Celsius (273.15 K). In addition to the natural system, human activities have had a profound impact on the energy budget of the earth system. To some extent, air pollutants emitted by anthropogenic activities also affect the atmospheric radiative transfer processes and result in environmental effects and public health impact.

  Following this deepened understanding of EMR, wavelength-dependent analyses for remote sensing data collection are often highlighted with respect to the given band specifications in the literature. Remote sensing sensor design based on specified bands and center wavelengths thus becomes feasible for collecting various images for processing, information extraction, and interpretation. Depending on the goals of each individual application, satellites onboard different sensors may be regarded as a cohesive task force to achieve a unique mission for earth observation and environmental monitoring. It is the aim of this chapter to establish a foundation by introducing a series of basic concepts and methods along this line.

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  Contemporary Climatology

  • P.J. Robinson, Ann Henderson-Sellers(Authors)
  • 2014(Publication Date)
  • Routledge

    (Publisher)

  All bodies radiate at a large number of wavelengths. The complete set of possible wavelengths is called the electromagnetic spectrum (Figure 2.2). Climatologically important radiation is within the range 0.1 to 100 µm. The human eye responds to a very small portion of this region, which we call visible light. Our sense of colour depends on the wavelength of the light our eyes receive. Wavelengths around 0.40 µm give violet light. As wavelength increases we see the colours of the rainbow until at 0.70 µm we reach red light. Regions adjacent to this visible portion are given names associated with the nearest colour. The region with wavelengths slightly shorter than 0.40 µm is termed ultraviolet, while radiation with wavelengths longer than ~1.0 µm (and ≤1 mm) is termed infrared radiation. Figure 2.1 The energy balance of planet Earth. The incident solar irradiance is shown as 100 units. Thus the reflected, transmitted and absorbed components of both incident solar and emitted terrestrial radiation are percentages of this value. For example, the diagram shows a globally averaged value of surface albedo of 4/26 or 0.15. The short-wave radiation (a) is balanced by the long-wave radiation (b) at (i) the top of the atmosphere (the planetary budget); (ii) the atmosphere; and (iii) the surface. Note the major contribution to the planetary albedo (20%) made by clouds, which also make a significant contribution to the emitted radiation. Despite the importance of these features the primary site of absorption of short-wave radiation is the surface. Figure 2.2 The electromagnetic spectrum, emphasising the wavelength regions of importance for climatology, which range from ~0.1 to ~100 µm. The lower part of the diagram shows atmospheric absorption over this wavelength range

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  Non-ionizing Radiation Protection

  Summary of Research and Policy Options

  • Andrew W. Wood, Ken Karipidis, Andrew W. Wood, Ken Karipidis(Authors)
  • 2017(Publication Date)
  • Wiley

    (Publisher)

  Part II Ultraviolet (UV) Light Passage contains an image

  Chapter 4 UVR and Short-Term Hazards to the Skin and Eyes

  Colin Roy and Peter Gies

  Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Australia

  4.1 Introduction

  4.1.1 UV A, B, and C

  Ultraviolet radiation (UVR) is part of the solar electromagnetic radiation spectrum, which includes visible radiation (wavelength range 400–770 nm) and infrared radiation (wavelengths >770 mm). The UVR region covers the wavelength range 100–400 nm and consists of three subregions, UVA (315–400 nm), UVB (280–315 nm), and UVC (100–280 nm) as defined by the International Non-Ionizing Radiation Committee (INIRC) of the International Radiation Protection Association (IRPA) and the Commission International de l' Eclairage (IRPA/INIRC, 1985 and the CIE, 1998).

  In general, only UVR in the range 200–400 nm can have a direct interaction with living organisms, since at wavelengths shorter than 200 nm, UVR is strongly absorbed by oxygen in the air. The penetration depth of UVR into human tissue is between 0.1 and 1 mm, so the organs at risk are the skin and the eyes. UVR has shorter wavelengths and thus more energetic photons than visible light and hence is capable of producing more damage when absorbed in biological tissue.

  4.1.2 Action Spectra

  The action spectrum is a measure of the effectiveness of different wavelengths of radiation in causing a photobiological process. The two most widely used action spectra are those for the skin and eyes (ICNIRP, 2004) and the skin (CIE, 1998), and these are shown in Figure 4.1

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  Crime Scene Photography

  • Edward M. Robinson(Author)
  • 2009(Publication Date)
  • Academic Press

    (Publisher)

  Chapter 7

  Ultraviolet, Infrared, and Fluorescence

  Contents

  The Electromagnetic Spectrum (EMS) Ultraviolet Light (UV) Infrared Light (IR) on the Electromagnetic Spectrum Visible Light Fluorescence Summary

  Learning Objectives

  On completion of this chapter, you will be able to …

  1. Explain the various results of light striking different surfaces. 2. Explain where on the electromagnetic spectrum the UV range is located. 3. Explain various uses of UV light to visualize otherwise “invisible” evidence. 4. Explain where on the electromagnetic spectrum the visible light range is located. 5. Explain the Stokes shift. 6. Explain some of the different types of evidence that can be made to fluoresce so they can more easily be located and collected. 7. Explain where on the electromagnetic spectrum the IR wavelengths are located. 8. Explain several types of evidence that can be visualized in the IR range of the electromagnetic spectrum.

  Key Terms

  Electromagnetic spectrum Fluorescence Infrared light Luminescence Phosphorescence Photographic infrared range Ultraviolet light Visible light

  The Electromagnetic Spectrum (EMS)

  Figure 7.1 shows the typical wavelength design. The wavelengths of ultraviolet (UV), visible light, and infrared (IR) light are expressed in terms of nanometers (1 nm = one billionth of a meter from peak to peak).

  Figure 7.1 Wavelength and amplitude.

  Light on the Electromagnetic Spectrum

  Other forms of radiation on the electromagnetic spectrum include those with much shorter wavelengths (gamma rays and X-rays), as well as those with much longer wavelengths (microwave and radio waves).

  Most have heard the phrase “the speed of light.” Sometimes this is explained with a reference to lightning. Because the speed of light (generally considered roughly 300,000,000 meters per second or 186,000 miles per second) is much faster than the speed of sound (generally considered 1120 feet per second or 761 miles per hour), you will see a lightning flash first; and then, depending on the distance of the lightning, the sound of the lightning can arrive several seconds later. Because the speed of light is so fast, and the distances you can see on earth relatively short, the “seeing” of light coming from any object on the earth appears “instantaneous.”

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  Atmosphere, Clouds, and Climate

  • David Randall(Author)
  • 2012(Publication Date)
  • Princeton University Press

    (Publisher)

  2 RADIATIVE ENERGY FLOWS THE EARTH'S RADIATION BUDGET

  ELECTROMAGNETIC RADIATION IS (ALMOST) THE ONLY way that the Earth can exchange energy with the rest of the universe.1 The radiation can be divided into categories, by wavelength:

   

  UV radiation, roughly from 0.1 to 0.4 μm, which is emitted by the Sun, absorbed in the stratosphere where it promotes the creation of ozone, and damaging to living things when it reaches the Earth's surface

  Visible light, roughly from 0.4 to 0.8 μm, which contains most of the Sun's energy output and is important for photosynthesis in plants and for human sight Near-infrared radiation, roughly from 0.8 to 4 μm, which is emitted by the Sun Thermal infrared radiation, roughly from 4 to 50 μm, which is emitted by the Earth and is the Earth's primary way of returning energy to space  

  Other wavelengths (e.g., X-rays and radio waves) are only very weakly emitted by the Sun (and the Earth) and are not important for the Earth's climate. As discussed at length below, averaged over the Earth and averaged over a year, the solar radiation absorbed is very nearly equal to the infrared radiation emitted back to space. The Earth is close to energy balance.

  SOLAR RADIATION

  The Sun provides an intense supply of electromagnetic radiation from a small, point-like patch of sky, that is, a small solid angle. The incoming solar radiation at the top of the atmosphere is called the “insolation,” or the “solar irradiance.” It is also called the “solar constant,” and in fact the Sun is a remarkably but not perfectly constant energy source. Calibrated measurements from satellites, which have been available since about 1980, show that, during the past 30 years, the total rate of energy output by the Sun has varied by only about ±0.1% or about ±1 W m-2

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