Electromagnetic spectrum lowest to highest,dungeon survival guide 3.5 pdf download,how to survive a disaster time magazine - Step 2

My last post discussed the nature of light, and that our current understanding is that light can be thought of as an electromagnetic wave carrying varying amounts of energy expressed by different wavelengths, or frequencies. The electromagnetic spectrum takes us all the way from the radio waves that we tune into while we’re driving in the car, to the light our eyes can actually see, to high-energy waves that can tear apart atoms. The lowest energy (lowest frequency, longest wavelength) types of electromagnetic energy are on the left, with the highest-energy (highest frequency, shortest wavelength) types of the right. It may surprise you that radio waves and microwaves are electromagnetic radiation just the same as visible light.
X-rays – This category of radiation has frequencies higher than UV, and like UV can literally tear molecules apart. Gamma – There is quite a bit of overlap in terms of frequency range with X-rays, with the only real distinction being that gamma rays originate from the nucleus of an atom. When it comes to electromagnetic radiation, it’s same shit, different pile (actually, it’s one continuous pile). Enter your email address to subscribe to this blog and receive notifications of new posts by email. List three “rules of thumb” that apply to the different frequencies along the electromagnetic spectrum. Explain why the higher the frequency, the shorter the wavelength of an electromagnetic wave. Draw a simplified electromagnetic spectrum, indicating the relative positions, frequencies, and spacing of the different types of radiation bands. List and explain the different methods by which electromagnetic waves are produced across the spectrum. In this module we examine how electromagnetic waves are classified into categories such as radio, infrared, ultraviolet, and so on, so that we can understand some of their similarities as well as some of their differences. Thus, for all electromagnetic waves, the greater the frequency, the smaller the wavelength. High-frequency electromagnetic waves are more energetic and are more able to penetrate than low-frequency waves.
High-frequency electromagnetic waves can carry more information per unit time than low-frequency waves.
The shorter the wavelength of any electromagnetic wave probing a material, the smaller the detail it is possible to resolve. The broad category of radio waves is defined to contain any electromagnetic wave produced by currents in wires and circuits.
There are many uses for radio waves, and so the category is divided into many subcategories, including microwaves and those electromagnetic waves used for AM and FM radio, cellular telephones, and TV. The lowest commonly encountered radio frequencies are produced by high-voltage AC power transmission lines at frequencies of 50 or 60 Hz. Extremely low frequency (ELF) radio waves of about 1 kHz are used to communicate with submerged submarines.
AM radio waves are used to carry commercial radio signals in the frequency range from 540 to 1600 kHz. A radio receiver tuned to have the same resonant frequency as the carrier wave can pick up the signal, while rejecting the many other frequencies impinging on its antenna. FM radio waves are also used for commercial radio transmission, but in the frequency range of 88 to 108 MHz. The wavelengths found in the preceding example are representative of AM, FM, and cell phones, and account for some of the differences in how they are broadcast and how well they travel. One benefit to these long AM wavelengths is that they can go over and around rather large obstacles (like buildings and hills), just as ocean waves can go around large rocks. Astronomers and astrophysicists collect signals from outer space using electromagnetic waves. One reason why we are sometimes asked to switch off our mobile phones (operating in the range of 1.9 GHz) on airplanes and in hospitals is that important communications or medical equipment often uses similar radio frequencies and their operation can be affected by frequencies used in the communication devices. For example, radio waves used in magnetic resonance imaging (MRI) have frequencies on the order of 100 MHz, although this varies significantly depending on the strength of the magnetic field used and the nuclear type being scanned. The wavelength of 100-MHz radio waves is 3 m, yet using the sensitivity of the resonant frequency to the magnetic field strength, details smaller than a millimeter can be imaged.
Microwaves are the highest-frequency electromagnetic waves that can be produced by currents in macroscopic circuits and devices.
Since it is possible to carry more information per unit time on high frequencies, microwaves are quite suitable for communications. How does the ubiquitous microwave oven produce microwaves electronically, and why does food absorb them preferentially? Water and some other constituents of food have a slightly negative charge at one end and a slightly positive charge at one end (called polar molecules).
The energy thereby absorbed results in thermal agitation heating food and not the plate, which does not contain water. Remove the rotating turntable or moving plate and place a cup of water in several places along a line parallel with the opening.
Microwaves generated by atoms and molecules far away in time and space can be received and detected by electronic circuits. The range of infrared frequencies extends up to the lower limit of visible light, just below red. We can examine radiant heat transfer from a house by using a camera capable of detecting infrared radiation. The relatively constant temperature of the Earth is a result of the energy balance between the incoming solar radiation and the energy radiated from the Earth.
Visible light is the narrow segment of the electromagnetic spectrum to which the normal human eye responds. Red light has the lowest frequencies and longest wavelengths, while violet has the highest frequencies and shortest wavelengths. Living things—plants and animals—have evolved to utilize and respond to parts of the electromagnetic spectrum they are embedded in.
During laser vision correction, a brief burst of 193-nm ultraviolet light is projected onto the cornea of a patient.
The energy from the laser light goes toward raising the temperature of the tissue and also toward evaporating it.
The lasers used for this eye surgery are excimer lasers, whose light is well absorbed by biological tissue.
Optics is the study of the behavior of visible light and other forms of electromagnetic waves.
When electromagnetic radiation interacts with objects about the same size as the wavelength or smaller, its wave nature becomes apparent.
When you light a match you see largely orange light; when you light a gas stove you see blue light. Ultraviolet means “above violet.” The electromagnetic frequencies of ultraviolet radiation (UV) extend upward from violet, the highest-frequency visible light. Solar UV radiation is broadly subdivided into three regions: UV-A (320–400 nm), UV-B (290–320 nm), and UV-C (220–290 nm), ranked from long to shorter wavelengths (from smaller to larger energies).
All UV radiation can damage collagen fibers, resulting in an acceleration of the aging process of skin and the formation of wrinkles. The tanning response is a defense mechanism in which the body produces pigments to absorb future exposures in inert skin layers above living cells. Repeated exposure to UV-B may also lead to the formation of cataracts in the eyes—a cause of blindness among people living in the equatorial belt where medical treatment is limited. A major acute effect of extreme UV exposure is the suppression of the immune system, both locally and throughout the body. Low-intensity ultraviolet is used to sterilize haircutting implements, implying that the energy associated with ultraviolet is deposited in a manner different from lower-frequency electromagnetic waves. Flash photography is generally not allowed of precious artworks and colored prints because the UV radiation from the flash can cause photo-degradation in the artworks.
If all of the Sun’s ultraviolet radiation reached the Earth’s surface, there would be extremely grave effects on the biosphere from the severe cell damage it causes. Unfortunately, today we are observing a depletion in ozone concentrations in the upper atmosphere. The UV radiation helps dissociate the CFC’s, releasing highly reactive chlorine (Cl) atoms, which catalyze the destruction of the ozone layer. A single chlorine atom could destroy ozone molecules for up to two years before being transported down to the surface. International concern over this problem led to the establishment of the “Montreal Protocol” agreement (1987) to phase out CFC production in most countries. Besides the adverse effects of ultraviolet radiation, there are also benefits of exposure in nature and uses in technology. When exposed to ultraviolet, some substances, such as minerals, glow in characteristic visible wavelengths, a process called fluorescence. In the case shown, an inner-shell electron (one in an orbit relatively close to and tightly bound to the nucleus) is ejected.
The second method by which an energetic electron creates an X-ray when it strikes a material is illustrated in [link]. A loss of kinetic energy implies an acceleration, in this case decreasing the electron’s velocity. In the 1850s, scientists (such as Faraday) began experimenting with high-voltage electrical discharges in tubes filled with rarefied gases. As described in Things Great and Small, there are two methods by which X-rays are created—both are submicroscopic processes and can be caused by high-voltage discharges. X-rays have adverse effects on living cells similar to those of ultraviolet radiation, and they have the additional liability of being more penetrating, affecting more than the surface layers of cells. The widest use of X-rays is for imaging objects that are opaque to visible light, such as the human body or aircraft parts. The ability of X-rays to penetrate matter depends on density, and so an X-ray image can reveal very detailed density information.
The use of X-ray technology in medicine is called radiology—an established and relatively cheap tool in comparison to more sophisticated technologies. Because they can have wavelengths less than 0.01 nm, X-rays can be scattered (a process called X-ray diffraction) to detect the shape of molecules and the structure of crystals. X-rays are also used as a precise tool for trace-metal analysis in X-ray induced fluorescence, in which the energy of the X-ray emissions are related to the specific types of elements and amounts of materials present. Soon after nuclear radioactivity was first detected in 1896, it was found that at least three distinct types of radiation were being emitted. Gamma rays have characteristics identical to X-rays of the same frequency—they differ only in source.
Infrared telescopes need to have their detectors cooled by liquid nitrogen to be able to gather useful signals. The most famous of these infrared sensitive telescopes is the James Clerk Maxwell Telescope in Hawaii.
The Hubble Space Telescope (launched in 1990) gathers ultraviolet radiation as well as visible light.
The electromagnetic spectrum is separated into many categories and subcategories, based on the frequency and wavelength, source, and uses of the electromagnetic waves. Any electromagnetic wave produced by currents in wires is classified as a radio wave, the lowest frequency electromagnetic waves. Infrared radiation lies below visible light in frequency and is produced by thermal motion and the vibration and rotation of atoms and molecules. Visible light is largely produced by electronic transitions in atoms and molecules, and is defined as being detectable by the human eye. Ultraviolet radiation starts with frequencies just above violet in the visible range and is produced primarily by electronic transitions in atoms and molecules. X-rays are created in high-voltage discharges and by electron bombardment of metal targets.
Gamma rays are nuclear in origin and are defined to include the highest-frequency electromagnetic radiation of any type. If you live in a region that has a particular TV station, you can sometimes pick up some of its audio portion on your FM radio receiver. Explain why people who have the lens of their eye removed because of cataracts are able to see low-frequency ultraviolet. How do fluorescent soap residues make clothing look “brighter and whiter” in outdoor light?
Illustrate that the size of details of an object that can be detected with electromagnetic waves is related to their wavelength, by comparing details observable with two different types (for example, radar and visible light or infrared and X-rays). Make a list of some everyday objects and decide whether they are transparent or opaque to each of the types of electromagnetic waves. Your friend says that more patterns and colors can be seen on the wings of birds if viewed in ultraviolet light. The rate at which information can be transmitted on an electromagnetic wave is proportional to the frequency of the wave. In an MRI scan, a higher magnetic field requires higher frequency radio waves to resonate with the nuclear type whose density and location is being imaged. Laser vision correction often uses an excimer laser that produces 193-nm electromagnetic radiation. Find the frequency range of visible light, given that it encompasses wavelengths from 380 to 760 nm.
Some radar systems detect the size and shape of objects such as aircraft and geological terrain. Distances in space are often quoted in units of light years, the distance light travels in one year. Yesterday’s article, Bullshit Alert – Since 11 March 2011, If You’ve Ever Even Heard of Japan, You’ve Been Exposed, introduced this and the article that follows, and explained my motivation for writing both.
Media coverage of the recent nuclear reactor explosions and linked disasters in Japan has not taken the science of the situation with anything approaching the degree of seriousness it deserves. While all this is going on, an atmosphere of apprehension builds, even among people who have nothing to fear from the situation. The shelter never got built, but years later I discovered that booklet in an envelope with still more documentation of similar ilk, and asked my father about it. Nuclear reactor accidents are not common, but with the expansion of populations in the world will come a drive to increase the number of nuclear power plants in service.
For analytical purposes, it is sometimes more convenient to treat energy travelling by radiation as a wave and at other times as a particle. We all know from school science class that the spectrum is what we see when sunlight passes through a glass prism.
The visible spectrum is part of the all encompassing electromagnetic spectrum which identifies all frequencies of energy, from lowest to highest.
If you’ve ever set out to cultivate a sun tan, or worse yet had a sun burn, you know about the effects of ultraviolet light. Now, let’s say we send one person out under the same conditions, and use a magnifying glass to focus sunlight on a small area of their skin. From here on in, we’re going to focus our attention exclusively on ionizing radiation (the x-ray and gamma ray portion of the electromagnetic spectrum) because understanding the creation and effects of energy at this level is essential to grasping the health effects of exposure.
Purists will say that what follows is a gross oversimplification of atomic structure, but since my purpose here is to debunk radiation as it has come to be misrepresented in  popular culture, and I am only interested in its effects on living things like people, no more complication is necessary. Now let’s focus on thinking of radiation as a stream of particles instead of waves – remember my machine gun example earlier? When living cells are exposed to ionizing radiation, this phenomenon can result in the creation of unstable atoms or molecules that are highly chemically reactive, with resultant damage to vital molecular structures like DNA. Acute Radiation Syndrome (ARS), formerly called Radiation Sickness or Radiation Poisoning, results from exposure to ionizing radiation.


So, in the end, it’s pollutants released and dispersed by a nuclear disaster site that people living downwind of it have to deal with, and while these may represent a threat to health and safety and should be treated as highly toxic crap, they are not magical. Too heavy for me to post an intelligent comment or question, other than a very educated informative read !
Oh Leroy, when I write for my audience, I assume infinite ignorance and unlimited intelligence.
Electromagnetic radiation, such as light, is composed of particles called photons that travel through space in a wave motion (Fig. Figure 2: The electromagnetic spectrum, showing relative wavelengths and frequencies, with visible light expanded. As you can see from Figure 2, white light is not one of the colors that are a part of the visible spectrum.
A transmission diffraction grating is made up of a transparent material with regularly spaced grooves cut into it so that a beam of light passing through is separated out. When white light strikes an object, usually some of the radiation is reflected off of the object and some is absorbed. If instead of shining white light on a solid object, we shine it through a transparent solution, we will see a similar effect. Spectrophotometers are instruments that measure which wavelengths of light have been transmitted and absorbed by solutions, and also tells how much of the light has been absorbed.
White light from the light source will pass through the sample and some of the light will be absorbed. Radio: Your radio captures radio waves emitted by radio stations, bringing your favorite tunes. Microwave: Microwave radiation will cook your popcorn in just a few minutes, but is also used by astronomers to learn about the structure of nearby galaxies. Infrared: Night vision goggles pick up the infrared light emitted by our skin and objects with heat. Ultraviolet: Ultraviolet radiation is emitted by the Sun and are the reason skin tans and burns. X-ray: A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag. Electromagnetic radiation can be described in terms of a stream of mass-less particles, called photons, each traveling in a wave-like pattern at the speed of light. The short answer is that scientists don't like to use numbers any bigger or smaller than they have to. The wavelengths of ultraviolet, X-ray, and gamma-ray regions of the EM spectrum are very small.
The Earth's atmosphere stops most types of electromagnetic radiation from space from reaching Earth's surface. For long-term observations, however, it is best to have your detector on an orbiting satellite and get above it all!
We have learned to embed information in these low-energy waves by either frequency modulation (FM) or amplitude modulation (AM). As implied in the name, this category of radiation is higher in energy than violet light, and we can no longer see this radiation with our eyes.
However, on the higher end of the X-ray range, the energy is so high that the radiation doesn’t efficiently interact with the soft tissues of our bodies (it still does to a degree, and when it does it’s fierce). So, this is what powers nuclear power plants (along with other wavelengths), and what (mostly) comes blasting out of a nuclear bomb.
The next post will take a look at how electromagnetic energy is produced in the sun, and what the Earth is getting showered with. We will also find that there are many connections with previously discussed topics, such as wavelength and resonance. Among the many shared attributes of waves are propagation speed, frequency, and wavelength.
This module concentrates on EM waves, but other modules contain examples of all of these characteristics for sound waves and submicroscopic particles. Many of the characteristics of the various types of electromagnetic waves are related to their frequencies and wavelengths, as we shall see.
If the material is transparent to the particular frequency, then the wave can largely be transmitted. We normally associate these properties with visible light, but they do apply to all electromagnetic waves.
The ability of radio waves to penetrate salt water is related to their wavelength (much like ultrasound penetrating tissue)—the longer the wavelength, the farther they penetrate. The abbreviation AM stands for amplitude modulation, which is the method for placing information on these waves.
The receiver’s circuitry is designed to respond to variations in amplitude of the carrier wave to replicate the original audio signal. Thus the carrier frequencies of two different radio stations cannot be closer than 0.020 MHz. Since the waves must carry a great deal of visual as well as audio information, each channel requires a larger range of frequencies than simple radio transmission.
Note that these frequencies are those of free transmission with the user utilizing an old-fashioned roof antenna. The wavelengths are also related to other properties of these electromagnetic waves, as we shall see.
Thus a very large antenna is needed to efficiently broadcast typical AM radio with its carrier wavelengths on the order of hundreds of meters. FM and TV are best received when there is a line of sight between the broadcast antenna and receiver, and they are often sent from very tall structures. A common problem for astrophysicists is the “pollution” from electromagnetic radiation pervading our surroundings from communication systems in general.
MRI is an important medical imaging and research tool, producing highly detailed two- and three-dimensional images. This is a good example of an exception to a rule of thumb (in this case, the rubric that details much smaller than the probe’s wavelength cannot be detected).
They are, for example, a component of electromagnetic radiation generated by thermal agitation.
Most satellite-transmitted information is carried on microwaves, as are land-based long-distance transmissions. By detecting and timing microwave echoes, radar systems can determine the distance to objects as diverse as clouds and aircraft. The range of microwave frequencies is specially selected so that the polar molecules, in trying to keep orienting themselves with the electric field, absorb these energies and increase their temperatures—called dielectric heating.
Microwaves will penetrate more than shorter wavelengths into tissue and so can accomplish “deep heating” (called microwave diathermy). Assuming that the power output of the oven is 1000 W, calculate the efficiency of the heat-transfer process. Deep space acts like a blackbody with a 2.7 K temperature, radiating most of its energy in the microwave frequency range.
Infrared radiation is generally produced by thermal motion and the vibration and rotation of atoms and molecules.
In fact, infrared means “below red.” Frequencies at its upper limit are too high to be produced by accelerating electrons in circuits, but small systems, such as atoms and molecules, can vibrate fast enough to produce these waves.
Night-vision scopes can detect the infrared emitted by various warm objects, including humans, and convert it to visible light.
Reconnaissance satellites can detect buildings, vehicles, and even individual humans by their infrared emissions, whose power radiation is proportional to the fourth power of the absolute temperature. About half of the solar energy arriving at the Earth is in the infrared region, with most of the rest in the visible part of the spectrum, and a relatively small amount in the ultraviolet. Visible light is produced by vibrations and rotations of atoms and molecules, as well as by electronic transitions within atoms and molecules. Blackbody radiation from the Sun peaks in the visible part of the spectrum but is more intense in the red than in the violet, making the Sun yellowish in appearance. Visible light is the most predominant and we enjoy the beauty of nature through visible light. For example, observable detail is limited by the wavelength, and so visible light can never detect individual atoms, because they are so much smaller than its wavelength.
It is estimated that as many as 20% of adults will develop skin cancer over the course of their lifetime. Because there is so little UV-B and UV-C reaching the Earth’s surface, sunburn is caused by large exposures, and skin cancer from repeated exposure.
Basically UV-B radiation excites DNA molecules, distorting the DNA helix, leading to mutations and the possible formation of cancerous cells.
Cataracts, clouding in the eye’s lens and a loss of vision, are age related; 60% of those between the ages of 65 and 74 will develop cataracts. Often artworks will have an extra-thick layer of glass in front of them, which is especially designed to absorb UV radiation. However, developing-country participation is needed if worldwide production and elimination of CFCs is to be achieved.
Vitamin D production in the skin (epidermis) results from exposure to UVB radiation, generally from sunlight. It is also used in sterilizing workspaces and tools, and killing germs in a wide range of applications. So-called black lights emit ultraviolet to cause posters and clothing to fluoresce in the visible. A short time later, another electron is captured and falls into the orbit in a single great plunge. It was later found that these discharges created an invisible, penetrating form of very high frequency electromagnetic radiation. While the low-frequency end of the X-ray range overlaps with the ultraviolet, X-rays extend to much higher frequencies (and energies). In humans, the risk of cell damage is weighed carefully against the benefit of the diagnostic information obtained. X-ray diffraction was crucial to Crick, Watson, and Wilkins in the determination of the shape of the double-helix DNA molecule.
The entire electromagnetic spectrum is used by researchers for investigating stars, space, and time. Since infrared radiation is predominantly from thermal agitation, if the detectors were not cooled, the vibrations of the molecules in the antenna would be stronger than the signal being collected.
The earliest telescopes, developed in the seventeenth century, were optical telescopes, collecting visible light. Radio waves are divided into many types, depending on their applications, ranging up to microwaves at their highest frequencies.
Their lowest frequencies overlap the ultraviolet range but extend to much higher values, overlapping at the high end with gamma rays. Is this consistent with the fact that laser telephone transmission at visible frequencies carries far more conversations per optical fiber than conventional electronic transmission in a wire? What effect does going to a larger magnetic field have on the most efficient antenna to broadcast those radio waves? This wavelength is extremely strongly absorbed by the cornea and ablates it in a manner that reshapes the cornea to correct vision defects. If you haven’t yet read my intro, please go and do so now before coming back here and moving forward. By the time that conversation took place, I had developed a voracious interest in science – most particularly physics, and military history, from all of which I had come to understand the concepts of nuclear fission and nuclear fusion. White light is split into its component colours and ends up a beautiful display on the wall, always projected in the same order that can easily be remembered by the name of the fictional professor, Roy G. This means that its energy level and frequency put it off the left hand margin of our visible spectrum chart. In mere seconds, if it takes that long, our unhappy subject will experience searing pain and blistering tissue damage. Ionizing radiation has sufficient energy to strip electrons from their safe little orbits by simply blowing them away.
When this occurs, the organism’s ability to repair itself and develop new, healthy cells can become impaired resulting in autoimmune disorders and cancer. Even relatively low levels of exposure can produce gastrointestinal symptoms like nausea and vomiting, while more extensive exposures can present as lowered blood cell count and neurological damage. What they are really referring to is particles of matter that are themselves radioactive, becoming air or waterborne, and making their way onto inhabited areas or into food and water supplies. Gases may disperse, but if they are vapours they will condense after cooling and likewise settle.
The image below shows where you might encounter each portion of the EM spectrum in your day-to-day life.
They are produced in different processes and are detected in different ways, but they are not fundamentally different. Most of the radio part of the EM spectrum falls in the range from about 1 cm to 1 km, which is 30 gigahertz (GHz) to 300 kilohertz (kHz) in frequencies. Infrared astronomers use microns (millionths of a meter) for wavelengths, so their part of the EM spectrum falls in the range of 1 to 100 microns.
Instead of using wavelengths, astronomers that study these portions of the EM spectrum usually refer to these photons by their energies, measured in electron volts (eV). This illustration shows how far into the atmosphere different parts of the EM spectrum can go before being absorbed. There is only a very small part of the spectrum that our eyes can detect and that we consider ‘light’.  In reality, the window that is visible light is actually much smaller than what is depicted above, and is actually a tiny sliver of the entire spectrum. So, all the water in food gets hot in your microwave oven, and that’s what transmits the heat to the rest of the food. The energy inherent in ultraviolet is where things can start to cause serious ‘damage’ and why radiation from the sun gets a bad rap.
A brief overview of the production and utilization of electromagnetic waves is found in [link].
What is not obvious is that something that is transparent to light may be opaque at other frequencies. Since salt water is a good conductor, radio waves are strongly absorbed by it, and very long wavelengths are needed to reach a submarine under the surface. An FM receiver is tuned to resonate at the carrier frequency and has circuitry that responds to variations in frequency, reproducing the audio information. So an AM receiver would interpret noise added onto the amplitude of its carrier wave as part of the information. Satellite dishes and cable transmission of TV occurs at significantly higher frequencies and is rapidly evolving with the use of the high-definition or HD format. FM, TV, and mobile phone antennas themselves are much smaller than those used for AM, but they are elevated to achieve an unobstructed line of sight.
Even everyday gadgets like our car keys having the facility to lock car doors remotely and being able to turn TVs on and off using remotes involve radio-wave frequencies.
Radio waves are broadcast, absorbed, and reemitted in a resonance process that is sensitive to the density of nuclei (usually protons or hydrogen nuclei). The thermal motion of atoms and molecules in any object at a temperature above absolute zero causes them to emit and absorb radiation. A clear line of sight between transmitter and receiver is needed because of the short wavelengths involved. A Doppler shift in the radar echo can be used to determine the speed of a car or the intensity of a rainstorm.
In 1964, Penzias and Wilson detected this radiation and eventually recognized that it was the radiation of the Big Bang’s cooled remnants.


More mundanely, we use infrared lamps, some of which are called quartz heaters, to preferentially warm us because we absorb infrared better than our surroundings. Most lasers used for this type of eye surgery have an average power rating of about one watt. When electromagnetic radiation, such as visible light, interacts with objects that are large compared with its wavelength, its motion can be represented by straight lines like rays. Physical or wave optics is the study of such situations and includes all wave characteristics. The wavelengths of ultraviolet extend from 400 nm down to about 10 nm at its highest frequencies, which overlap with the lowest X-ray frequencies. Some studies indicate a link between overexposure to the Sun when young and melanoma later in life. However, treatment is easy and successful, as one replaces the lens of the eye with a plastic lens. The hole is more centered over the southern hemisphere, and changes with the seasons, being largest in the spring. A number of studies indicate lack of vitamin D can result in the development of a range of cancers (prostate, breast, colon), so a certain amount of UV exposure is helpful. Ultraviolet is also used in special microscopes to detect details smaller than those observable with longer-wavelength visible-light microscopes.
These collisions transfer kinetic energy from the electron to the electrons and atoms in the material. Because of their effect on rapidly dividing cells, X-rays can also be used to treat and even cure cancer.
However, questions have risen in recent years as to accidental overexposure of some people during CT scans—a mistake at least in part due to poor monitoring of radiation dose. The amount of information in a simple X-ray image is impressive, but more sophisticated techniques, such as CT scans, can reveal three-dimensional information with details smaller than a millimeter. During World War I, mobile X-ray units, advocated by Madame Marie Curie, were used to diagnose soldiers. As noted earlier, Penzias and Wilson detected microwaves to identify the background radiation originating from the Big Bang. Explain how the strong absorption helps concentrate the energy in a thin layer and thus give greater accuracy in shaping the cornea. I tried to explain the concepts to my father, but by this time he had spent far too many years marinating in the belief that it was all so very far beyond him.
Knowledge is power, and your government neither can nor will save you and that which you treasure. Radiation is not a thing, it’s a process, and one of three ways that energy gets from one place to another (the other two being conduction and convection, neither of which apply to the topic under discussion).
As with ultraviolet, infrared cannot be seen by the unaided human eye, but it can be detected by other senses as heat. One person goes outside and exposes their unprotected bare skin to the direct rays of the sun for a period of 5 minutes.
In this case, even brief exposure can have massive effects because the intensity of radiation is so high. For purposes of our discussion here, only the labels representing the type of radiation (radio through visible on up to gamma rays) and the wave diagram matter. The end result is a loss of electrical balance in the atom because there are no longer enough negative electrons to counterbalance the positive protons in the nucleus. If you’ve ever seen a major fire, you know how high, far, and wide the heat plume can carry the ash. Areas downwind of a burning reactor are evacuated because radioactive material is released, not radiation itself. The other categories of electromagnetic radiation interact with the environment and us differently, but they’re fundamentally the same phenomenon as visible light. These guys aren’t dangerous since the strength of the signals we use for communication are weak (very few waves, relatively speaking), and interact with matter very modestly. Cell phones transmit information on the low-energy side of the microwave band, but at very low signal strengths.
This type of radiation has enough energy to get pretty much everything vibrating and rotating and getting HOT.
On the low-energy side of the UV spectrum, if an electron absorbs this type of radiation (creating an ion), it can get stripped off its host atom, which changes the behaviour of the atom. Small and controlled doses are used in medical imaging and cancer therapy where, similar to X-rays, the benefits of the radiation dose are hoped to outweigh the damage incurred. The wave can also be absorbed by the material, indicating that there is some interaction between the wave and the material, such as the thermal agitation of molecules. For example, ordinary glass is transparent to visible light but largely opaque to ultraviolet radiation. An FM receiver can be made to reject amplitudes other than that of the basic carrier wave and only look for variations in frequency. In order to prevent interference between all these electromagnetic signals, strict regulations are drawn up for different organizations to utilize different radio frequency bands.
Sophisticated radar systems are used to map the Earth and other planets, with a resolution limited by wavelength. How does the size of the holes in the grid compare with the wavelengths of microwaves used in microwave ovens? We say the atoms and molecules are excited when they absorb and relax when they emit through electronic transitions.
It was recognized as early as 1801 by Johann Ritter that the solar spectrum had an invisible component beyond the violet range.
Despite very little UV-B reaching the Earth’s surface, there are substantial increases in skin-cancer rates in countries such as Australia, indicating how important it is that UV-B and UV-C continue to be absorbed by the upper atmosphere. This depletion is attributed to the breakdown of ozone molecules by refrigerant gases called chlorofluorocarbons (CFCs).
Since this is a high-voltage discharge, the electron gains sufficient energy to ionize the atom. Since the orbits of the atom are unique to the type of atom, the energy of the X-ray is characteristic of the atom, hence the name characteristic X-ray.
Radio telescopes such as the Arecibo Radio Telescope in Puerto Rico and Parkes Observatory in Australia were designed to detect radio waves. The LFM archives still contain a copy of that Canadian Government classic and number one title in the Blueprint For Survival series, Your Basement Fallout Shelter. The science of understanding the effects of anything from a nuclear reactor accident to a hospital x-ray is completely within the grasp of the average person. When energy is transported by radiation, particles or waves travel through a medium (like air, glass, or any other material that is more or less transparent to the energy) or space. If we look at these energy levels as particles instead of waves that are either slower or faster to arrive on the beach, think of a little machine gun firing tiny bullets. It’s called ULTRA-violet because its energy level and frequency lies BEYOND violet, which would put it off the right hand margin of our visible spectrum chart. Note that going from left to right, waves start out more widely spaced, and become progressively closer together as we move upward in frequency and therefore higher energy level.
In the center we have the nucleus which is made up of one or more neutrons which have no electrical charge, and one or more protons which have a positive electrical charge.
It must be understood that some of the people working right now to clean up the nuclear disaster sites in Japan are doing so in the full knowledge that they are committing suicide. If it hits you square in the eye from close range it’ll have a big effect when it temporarily blinds you. In some cases, particularly with forest fires, new burns can be ignited by coals carried upward on the plume and later dropped sometimes miles away. It’s most often either going to arrive as particles, vapour, or gas suspended in air or water, be encountered as solid particles or droplets condensed from vapour that have coated exposed surfaces as with any other dust, dirt, or mist, and as dissolved and therefore invisible chemicals in water and other liquids that have been open to the air. Light is broadly categorized into about eight different types of radiation, as shown above.
Other than being able to heat certain substances if the signal strength is high enough, microwave radiation is quite safe. Hot objects, like the element on your stove, radiate a lot of infra-red energy, and even human bodies radiate at about the middle of the infrared range. Increasing the energy within this range, and molecules are torn apart (pulling atoms away from each other). Human skin is opaque to visible light—we cannot see through people—but transparent to X-rays.
They are created by many astronomical phenomena, and their study has revealed much about nature on the largest scales.
Other channels called UHF (for ultra high frequency) utilize an even higher frequency range of 470 to 1000 MHz. Exposures (with no sunscreen) of 10 minutes a day to arms, face, and legs might be sufficient to provide the accepted dietary level. Since the process is random, a broad spectrum of X-ray energy is emitted that is more characteristic of the electron energy than the type of material the electron encounters. Our copy is the one ordered by my parents back in the day, in the wake of the Cuban Missile Crisis, and quietly pored over through many a long night, as they agonized over how to balance the burden of raising a family against that of building and stocking something that might represent the critical difference between life and death.
This means that there is a source that is radiating these particles or waves, and as they travel out from the source they either pass through or are absorbed by open space or matter along the way.
The same effect is at work when sunlight passing through airborne water droplets blesses our eyes with a rainbow.
Not the visible part, but we can certainly detect it and put it to work, as evidenced by the number of cellular phones around. The red bullets hit the target at a slower rate than the violet ones that hit with greater frequency.
Being invisible doesn’t make its effects any less real, and its energy level even in this minor league within the spectrum, is something we all know is only to be ignored at our peril. At the end, each person was exposed to the same radiation intensity, but the one with the longest interval of exposure will experience the greatest effect and will most likely experience sun burn.
An unbridled reactor core can generate heat that would make a forest fire pale in comparison, and as with any physical, non-nuclear ignition comes production of gases and particles. Solid, liquid, or gas, radioactive pollutants can best be understood as consisting of a multitude of minuscule emitters of dangerously high energy, but the size of each, and the kinds of radioactive materials of which they’re made, limits the amount of radiation you will absorb for a given period of exposure because some reactor produced isotopes are more energetic than others, and unlike a large radiated energy source like a reactor core itself, the pollutant particles it releases during an accident are more dispersed.
This explains the colours in the rainbow (ROYGBIV – red, orange, yellow, green, blue, indigo, violet).
For the most part, the entire UV range is split up into the subcategories UV-A, UV-B, and UV-C. A bit of radiation damage in the soft tissues does happen, but the X-rays are finely tuned to minimize this, and the benefits (hopefully) outweigh the costs. To put it simply, energy is radiated by a source, travels in a straight line at the speed of light, and will attempt to pass through anything in its path.
When wrapping your mind around the concept of frequency and waves, think about waves lapping on a beach. As with ultraviolet, the effects of exposure can range from wonderful to catastrophic, depending on two things – intensity and exposure. The line between the two is found when the energy delivered by the radiation is sufficient to strip electrons from atoms or molecules (I’ll explain that in a minute), rendering them positively charged. In a stable atom, the number of electrons equals the number of protons, so their mutual positive and negative charges cancel one another out leaving the entire atom in balance with no net electrical charge at all. Radioactive material like the Uranium in a Japanese nuclear reactor emits radiation in the high end of the electromagnetic spectrum, but it radiates it no differently than a white hot coal radiates heat and light. Mix radioactive dust into the water though, and you have a brew that is unsafe to drink because ingestion of the particles, even in solution, will irradiate the consumer from the inside. From this it’s clear that getting away from the actual disaster site is a first priority, but for most people affected, getting out of the path of everything pouring out of it runs a close second. The way water vapour scatters light is wavelength-dependent, so higher energy light gets scattered at a slightly larger angle then lower energy light, which spreads out the colours and creates a rainbow.
This travelling energy is radiation, whether it comes from an exposed nuclear reactor core or a beeswax candle. My point is to illustrate that the visible energy radiated by the sun, which we call light, consists, in fact, of seven distinct levels of energy – the visible spectrum. They may arrive slowly, languidly, and 30 seconds apart, or they may be more energetic and wash in at 5 second intervals because a boat just passed by.
This process is called ionization, and the electrically charged atoms created by it are called ions. Atoms can also combine to form more complex structures called molecules, one of which is DNA, the molecule that is the blueprint for every living thing on Earth. A can of beans coated in radioactive dust, once cleaned, and I mean cleaned, will be safe to eat.
All of this is why we see workers doing cleanup at a nuclear disaster site being decontaminated at the end of a shift. These subcategories have different interactions with matter, as will be explained in the coming posts. Step back far enough and you can still see the glow so you’re still receiving some level of radiation from it, but you can no longer feel the heat.
As with all sources of ionizing radiation, the best protection is to get as far away from it as possible, something that is made a lot easier when you know your enemy and how it operates.
Those fancy suits they wear don’t stop energy from radiation emitted by the reactor core and its byproducts, but they do prevent direct contact with and ingestion of the dust, dirt, vapour, and gases that are inevitably encountered on any accident cleanup site. Far from being something sinister and mysterious, radiation is absolutely essential to life on Earth. The same rules of measurement apply to all types of radiation, and while ionizing radiation presents a powerful risk of damage to living tissue, the rules of intensity and exposure still apply. The contaminants are therefore rinsed off with appropriate solvents before workers break the seal on their suits.
If you go out today and feel warmed by the Sun, it’s because your skin and clothing are absorbing energy delivered by the process of radiation. Also remember, as we saw in our sun burn experiment, even non-ionizing radiation can be harmful if treated with a lack of understanding and respect. This is the risk posed by being in close proximity to a highly concentrated source of ionizing radiation – a source that is referred to as radioactive. When you heat your dinner in a microwave oven, it heats because the water molecules in the food are absorbing energy delivered by the process of radiation. Tissue destruction occurs through simple proximity as living cells are irradiated and damaged on an atomic level.
When your dentist x-rays your teeth, the image he sees is possible because x-rays are delivered by the process of radiation, fired in a brief burst through your head, and are absorbed differently by your soft and bony tissues before they strike the imaging film where they produce a visible image because the intensity of x-ray radiation striking the film is greater where they passed through soft tissue and lesser where they passed through denser tissue, which simply casts more of a shadow. As we move further out from the the source however, radiation intensity rapidly diminishes to the point where it can no longer be detected. We see the world around us because visible radiation bounces off of objects in our field of view and into our eyes where its energy is absorbed and reacted to by the cells of our retinas.
Even though it can be the process by which energy lethal to living organisms is delivered, it is also the means by which such benign forms of energy as the light from our lamps and the radio signal from our favourite music station gets delivered.



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