24.02.2016
There are a few facts you need to know about sunlight to better understand its impact on the human body and our environment.
If we think of the rainbow, we see light can have different colors, ranging from violet to red.
UVB is known to be responsible for the long lasting tan one possibly gets when staying in the sun. Until today, scientists thought that only UVB was responsible for causing skin cancer but they had to realize that 10 to 100 times more UVA (compared to UVB) reaches the earth. But many remain unconvinced that the common alternative - compact fluorescent lamps (CFLs) - are up to the job.
Think those compact fluorescent bulbs are not as bright as the old-style lights they replaced?
The Lighting Industry Federation says the claims on the packaging are the nearest equivalent to the wattage of a soft white light bulb. But even branded bulbs don't always last as long as expected - this is because the lifespan given is an average. But that results in a 5:1 energy ratio between the two - a claim it says is an exaggeration when manufacturers use it. Ms Peck, of the Society of Light and Lighting, says CFLs have improved in recent years - they flicker less, and warm up faster. February 20, 2015industrial paintingcommercial painting maryland, commercial painting new jersey, commercial painting pennsylvaniaPennCoat, Inc. One of the most important industrial and commercial painting features the PennCoat looks for in exterior topcoats is protection from the Sun’s powerful ultraviolet (UV) radiation. UV light spans wavelengths from 400 to 10 nanometers, shorter than visible light wavelengths but longer than those for X-rays. Paints and coatings protect substrates from UV degradation through the use of specific additives that absorb UV light and render it harmless. One of our most commonly used aliphatic urethanes¬†is a multi-part aliphatic urethane system containing a resin (blocked cycloaliphatic diamine), a hardener, and a colorant (dipropylene glycol monomethyl ether acetate + coloring oxides).
Add important lessons to your Custom Course, track your progress, and achieve your study goals faster. Your eyes tell you that the Sun obviously delivers energy to Earth in the form of visible light. Before we look at the multispectral Sun, let's review some key ideas about the electromagnetic (EM) spectrum.
Visible light is the most familiar form of a type of energy called electromagnetic radiation. Light comes in different colors, spread across the rainbow of hues we call the visible spectrum. This depiction of electromagnetic spectrum shows several objects with size scales comparable to the wavelengths of the waves of different types of electromagnetic radiation. Credit: Image courtesy of NASA's "Living With a Star" program and the Center for Science Education at Space Sciences Laboratory, University of California at Berkeley. The graph below shows a simplified representation of the energy emissions of the Sun versus the wavelengths of those emissions. Credit: Image courtesy of the COMET program and the High Altitude Observatory at NCAR (the National Center for Atmospheric Research). Physicists use a concept called a "blackbody radiator" to explain how hot objects emit EM radiation of different wavelengths. This graph shows the distribution of the EM energy emitted by a "blackbody radiator" having a temperature of the surface of the Sun (approximately 5,800 kelvin).
This animation shows views of the Sun at various frequencies across the electromagnetic spectrum. However, since it is alternating current, the current reverses direction many times a second. This acts as a bottleneck, reducing the amount of power reaching the destination end of the cable. Ultraviolet light, also called UV radiation, is classified into three types by its wavelength: UVA ranges from 400 to 320 nm, UVB from 320 to 290 nm, and UVC from 290 to 200 nm. European legislation has already banned the manufacture and import of 100-watt incandescent bulbs. Liz Peck, of the Society of Light and Lighting, says this is because CFLs have a phosphor coating.
When a batch of bulbs is tested, they are turned on for three hours, then off for 20 minutes over and over again until half the batch fails. The European Commission, the Energy Saving Trust and manufacturers say CFLs use up to 80% less electricity than traditional bulbs.
Normally, the relatively high energy of UV photons is enough to partially strip electrons from the valence shell of organic compounds, creating reactive free radicals. If you think about it a bit, especially in terms of the choices you make about UV-A and UV-B protection when you shop for sunscreen or sunglasses, you'll also realize that you know that the Sun also bathes our planet in ultraviolet "light" or radiation.
If you are very familiar with the EM spectrum (most chemistry and physics teachers are), feel free to skim this section.
Photons of light from violet end of the spectrum have the highest energies and the highest frequencies, while red photons have lower energies and lower frequencies.
Beyond the UV portion of the spectrum lie the still shorter waves (with higher frequencies and greater energies) of X-rays.
Note that the range of wavelengths vary by many orders of magnitude, while the waves shown in this "cartoon" do not.
This is a very large file (38 megabytes), so it will probably take quite a while to download!
Although the Sun produces gamma rays as a result of the nuclear fusion process (see the diagram of the proton-proton chain on "The Solar Furnace" reading page), these super high energy photons are converted to lower energy photons before they reach the Sun's surface and are emitted out into space. This may seem surprising at first, since the visible region of the spectrum spans a fairly narrow range.
The y-axis shows the relative amount of energy emitted at a given wavelength (as compared to a value of "1" for visible light). Although a blackbody radiator is a mental construct, not a real object, many real objects behave almost like a blackbody radiator. An iron bar made of solid metal and a giant ball of gas-like plasma made of hydrogen and helium don't seem very similar, and you might not expect them to behave at all alike.


If we look at the Sun in visible or IR light, we will pretty much be observing the photosphere. These images show the Sun in the infrared, visible light, four different ultraviolet wavelengths, and in X-rays. These narrow wavelength "windows" in the EM spectrum are actually the "fingerprints" of specific elements at specific temperatures. The Website was developed in part with the support of UCAR and NCAR, where it resided from 2000 - 2010. But if the damage is too severe and the cells cannot regenerate, those damaged cells can turn into skin cancer. They also had to realize that although it has less energy, UVA radiation penetrates deeper into human skin than UVB. But are these as bright, long-lasting and energy efficient as is often claimed?The traditional incandescent bulb is on the way out. A guide to the amount of light given by a CFL bulb is given on its box as a comparison to the wattage of an incandescent bulb. While a branded bulb from a well-known manufacturer may indeed last the promised 10 years, one from a supermarket budget line may not.
There are other energy-saving options, she says, such as halogen tungsten lights which are about 30% more efficient than incandescent bulbs. Because it vibrates at a higher frequency than does visible light, it carries more energy per photon and in high amounts can damage paints and people. The energy per photon throughout the UV range starts at 3.10 electron volts and goes as high as 124 eV. In general, exterior coatings are tested by applying them to substrates and then subjecting them to high-intensity UV lamps. Watch the video to find out what these types of radiation are really doing to atoms, define ionization energy and identify ionization trends on the periodic table. If this is an area that you are less comfortable with, we've provided some links to further readings that you might want to browse. In some ways it behaves like a stream of particles (which we call "photons"), and in other ways it acts like a series of waves. Beyond the range of our vision are the longer wavelengths of the infrared and the shorter wavelengths of the ultraviolet regions of the electromagnetic spectrum. Waves that have wavelengths slightly shorter than purple light, and thus have slightly higher frequencies and higher energy levels, are called ultraviolet ("beyond violet", from the Latin ultra = "beyond") or UV "light" or radiation. Beyond X-rays lie the extremely short wavelength gamma rays, which have exceptionally high energies and frequencies.
For example, visible light waves are typically 100 time shorter than infrared waves, not just slightly shorter as depicted pictorially. And what a coincidence, that sunlight should be brightest in the range our eyes are capable of seeing! Nevertheless, the visible "surface" of the Sun behaves pretty much like an idealized blackbody radiator. Note how the two curves are virtually identical from the near ultraviolet to the radio wave regions, but are quite different in the far ultraviolet and X-ray regimes. Images taken in very narrow bands have the wavelengths of the associated waves noted (in nanometers). Hot gases and plasmas emit light (or UV radiation or X-rays) at very specific wavelengths, depending on the element involved and the temperature of that element.
As we'll see in later pages, different wavelengths of EM radiation behave differently when they reach Earth's atmosphere.
Fortunately our earth is surrounded by a defensive shield of gases which absorbs all of the UVC radiation and some of the UVA and UVB radiation.
European law means people will be encouraged to use longer-lasting, energy-efficient lights instead. It's worked out by comparing the best compact fluorescent lamp's wattage with the wattage of an equivalent incandescent bulb, says a spokeswoman for the European Commission.
John Henderson, an energy-use expert from the consultancy Building Research Establishment, says although CFLs are better than traditional bulbs, policy-makers should not draw simple conclusions from simple sums about their energy saving potential. Meanwhile, the Institute of Lighting Engineers is considering changing its estimate of the energy savings represented by CFLs from 80% to 70%.
And technology is developing fast, so it could be only a few years before people are lighting their homes with LED lights, which experts say have the potential to be more efficient than CFLs.
UV takes its toll on exterior structures by making materials brittle and causing color to fade. Much, but not all, UV radiation is absorbed by Earth’s ozone layer, and one reason PennCoat favors coatings with low volatile organic compound content is to help protect the delicate ozone layer.
Paint and coatings fortified with antioxidant UV stabilizers absorb UV rays and thus prevent them from forming free radicals. In this way, testers can induce over a decade of weathering in only a year. And commercial paints that perform will in this test are often granted the privilege of becoming a commercial painting top coat for most painting contractors. Since all colors of light (and all types of EM waves, for that matter) travel at the same speed, wavelength is inversely proportional to frequency (frequency is how often the "crest" of a wave passes by a given location). Moving in the other direction, out beyond the infrared portion of the EM spectrum, we find various types of radio waves. Note that the scale of the y-axis is logarithmic; each tick mark represents a hundred-fold increase in amount of energy as you move upward. The units of energy along the vertical axis are relative to the peak in the Sun's EM energy output in the visible light part of the spectrum, which is arbitrarily given the value of "1". At first, when the iron is not especially hot, it will not glow at all; but if you put your hand near it, you could feel the heat it was giving off. The radiation emitted from the Sun's atmosphere causes the Sun to behave differently than an ideal blackbody radiator. The photosphere is most prominent in the visible light images, while UV and X-ray views show details of the solar atmosphere.
The infrared view shows the lower chromosphere immediately above the photosphere, where temperatures are still relatively cool. For example, the IR image with a wavelength of 1,083 nm is produced by atoms of helium indicative of temperatures of a few thousand kelvin. Fortunately for us, most of the high energy X-rays and ultraviolet radiation are absorbed by our atmosphere far above our heads, preventing them from frying us.


The same with light ? some light has long waves and does not carry much energy, other light has short waves, very close together, that carry lots of energy which may be harmful (ultraviolet-light).
The rest of the UVA and UVB light, which passes through no matter if it is cloudy or sunny, can have different impacts on our skin. So there are enough reasons why you should always wear a sunscreen that protects you from UVA and UVB (so-called broad spectrum sunscreens). As no-one adds up the hours a light is on over its lifespan, this is translated as 10 years, on the assumption that the bulb will be on for an average of three hours a day. This is because the power factor of CFLs is low, which means a utility company needs to use more energy to get these lights to work, which can also cause disruptions in the power network. Long wavelength red waves have low frequencies; short wavelength purple waves have high frequencies. Likewise, just beyond the other end of the visible spectrum lie waves with wavelengths slightly longer that red light waves. All radio waves have longer wavelengths than infrared waves, and thus carry less energy and have lower frequencies.
At this relatively low temperature the iron radiates most of its energy in the IR portion of the spectrum, which we cannot see but which we can feel as heat. The graph below shows the theoretical radiation curve for a blackbody radiator with a temperature of 5,800 K. Recall how the temperature of the Sun gradually declined from 15 million K at the core to 5,800 K at the photosphere, but then surprisingly rose again to 3 million K in the Sun's outer atmosphere (the corona).
Note that almost all of these images are "false color" representations, since your eyes cannot see X-rays or ultraviolet or infrared "light". Most of the high energy photons that produce the UV and X-ray views come from higher up in the Sun's hot atmosphere. The 30.4 nm wavelength UV image is also produced by helium, but that helium has been ionized (stripped of one of its two electrons), which indicates that its temperature is somewhere in 60,000 to 80,000 kelvin range, and thus that it is somewhere around the boundary between the upper chromosphere and the hotter corona.
They do, however, transfer their energy to the atmosphere at various levels, which has implications for our climate.
New European regulations expected next year mean manufacturers will have to display lumens - a measure of light output - more prominently than wattage on bulb packaging. But as half the bulbs will fail before 10,000 hours, a shopper may be unlucky enough to pick a dud that will fail after just 2,000 hours. Later in this week we'll see what happens to these different types of energy when they reach Earth. These waves, which have even lower frequencies and carry somewhat less energy than red light, are called infrared ("below red", from the Latin infra = "below") or IR "light" waves.
Microwaves (yes, the kind employed in microwave ovens) are relatively short wavelength (and thus relatively high energy) radio waves.
Imagine that our species had "grown up" on a planet orbiting a star that gave off most of its energy in the ultraviolet region of the spectrum. As the iron gets warmer, it begins to glow deep red; the peak of its radiation has just moved into the lowest energy, longest wavelength portion of the visible spectrum just above the infrared. Notice that over much of the EM spectrum the Sun looks very much like a blackbody radiator. The high temperatures of the solar atmosphere, along with explosive phenomena like solar flares that further energize this region of the Sun, generate high energy UV and X-ray photons. Notice how the areas of the atmosphere above sunspots tend to be especially bright in the X-ray and UV views.
Also, as we'll see in the very next reading, the amount of radiation emitted by the Sun in various wavelengths is not completely constant over time.
However, the main manufacturers do their best to make bulbs that cluster around the average life mark, says the Lighting Industry Federation. Electromagnetic radiation from the Sun is the main source of energy that drives Earth's climate system.
High frequency, short wavelength purple light carries the most energy; low frequency, long wavelength red light carries the least energy.
Back when broadcast television signals were common, the waves that carried TV signals to our antennas were a type of radio wave.
Presumably, we would have evolved eyes that could see UV "light", for light of that sort is what would be most brightly illuminating our planet's landscapes.
As the iron grows hotter, its glow becomes orange and then yellow, as its peak emissions creep up the spectrum to higher energies and shorter wavelengths. Notice also that the Sun emits many more high-energy photons in the UV and X-ray regions of the spectrum than a blackbody radiator would. Furthermore, different wavelengths of UV and X-ray emissions come from different heights in the solar atmosphere, so we can view different levels of the Sun's atmosphere by looking at specific wavelengths of these UV and X-ray emissions. Sunspots are visible indicators of magnetic disturbances on the Sun that spawn high-energy phenomena such as solar flares and coronal mass ejections. The main upshot of all this is that different wavelength images allow us to see material at different temperatures on and above the Sun.
Short term events like solar flares can dramatically alter the levels of X-ray and UV emissions from the Sun over the course of a few minutes. The same sort of reasoning would apply to species that evolved on planets orbiting stars that emit most of their energy in the infrared; they would most likely evolve to have IR sensitive eyes. In many cases, this means that each different wavelength image provides us with a view of material at a different height within the solar atmosphere. Multi-year cycles in solar activity only slightly alter the amount of visible light the Sun emits (to the tune of 0.1%), but can change the levels of X-ray and UV emissions by a hundred-fold.
Continuously turning it off and on every 15 minutes, for example, will more than halve its expected lifespan. If you were to replace all the old-fashioned light bulbs with the modern low energy lamps, you might expect an 80% reduction - 800kWh.



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Comments Does ultraviolet light carries more energy than infrared radiation

  1. Jenifer
    One produced by Seche or any other between.
  2. Sevgi_Qelbli
    Blacklight lamps operate around 350-360nm hard glass lamps are designed to operate lamp anywhere.