September 16, 2011

Why Laughter May Be the Best Pain Medicine

Laughter with friends releases endorphins, the brain's "feel-good" chemicals

Laughing with friends releases feel-good brain chemicals, which also relieve pain, new research indicates.
Until now, scientists haven't proven that like exercise and other activities, laughing causes a release of so-called endorphins.
"Very little research has been done into why we laugh and what role it plays in society," study researcher Robin Dunbar, of the University of Oxford, said in a statement. "We think that it is the bonding effects of the endorphin rush that explain why laughter plays such an important role in our social lives."



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U.K. Researchers to Test "Artificial Volcano" for Geoengineering the Climate

An experiment starting next month in the U.K. will pump water one kilometer into the air to test a new climate-cooling method that eventually could deliver sunlight-reflective sulfate particles into the stratosphere


Next month, researchers in the U.K. will start to pump water nearly a kilometer up into the atmosphere, by way of a suspended hose.

The experiment is the first major test of a piping system that could one day spew sulfate particles into the stratosphere at an altitude of 20 kilometers, supported by a stadium-size hydrogen balloon. The goal is geoengineering, or the "deliberate, large-scale manipulation of the planetary environment" in the words of the Royal Society of London, which provides scientific advice to policymakers. In this case, researchers are attempting to re-create the effects of volcanic eruptions to artificially cool Earth.

                      Volcanic eruptions, like this one at Mount Pinatubo eruption in 1991, are known to have global cooling effects. In October, researchers will test a man-made volcano that might eventually be used as a temporary defense against the devastating effects of climate  change. Image: Wikimedia Commons


The $30,000 test, part of a project called Stratospheric Particle Injection for Climate Engineering (SPICE), is inspired by the 1991 eruption of Mount Pinatubo in the Philippines. That volcano spewed 20 million tons of sulfate particles into the atmosphere, cooling Earth by 0.5 degree Celsius for 18 months. If the British feasibility tests are successful, the balloon-and-hose contraption could be used to inject additional particles into the stratosphere, thereby reflecting more of the sun's energy back into space, and hopefully curbing some of the effects of global warming.
"This is one of the first times that people have taken geoengineering out of the lab and into the field," lead scientist Matthew Watson said Tuesday during a press conference in London. "We are still decades away—and I do mean decades—from doing real geoengineering." Watson said his team still needs to determine which substances would work best at reflecting light, how much is needed to have an effect, and the possible unintended consequences of injecting the particles into the atmosphere, such as acid rain, ozone depletion or weather pattern disruption.
October's tests will mainly focus on whether the balloon-and-hose design could be an effective method to deliver the sunlight-reflecting particles. At an airfield in Norfolk, England, that is no longer in use, a helium blimp will hoist a regular pressure-washer hose one kilometer off the ground. An off-the-shelf pressure washer will pump up 1.8 liters of tap water per minute, to a maximum of 190 liters, says Hunt, which will evaporate or fall down to the ground locally. The researchers will monitor the performance of the system, and use the data to design the larger 20-kilometer-high setup.
In the past scientists have proposed similar atmospheric delivery methods using guns, airplanes, rockets and chimneys. In 2009 Russian scientists even tested airplane delivery on a small scale. But Hugh Hunt, a SPICE engineer at the University of Cambridge, said the balloon-and-hose design appears to be the most cost-effective option. Even when scaled up, the team expects the simple design to cost around $5 billion, in comparison with the $100 billion needed to launch thousands of high-altitude aircraft.
The water tests are expected to be harmless, but several environmental groups have criticized the plan—and geoengineering in general. Last year, the United Nation's Convention on Biological Diversity issued a statement forbidding geoengineering research that may impact biodiversity. The U.K. accepted that statement, but the SPICE experiment does not violate any international agreements due to its small scale, says Jason Blackstock, a physicist at Canada's Center for International Governance Innovation.
Whereas Hunt agrees that such research is lacking, he said that the team needs real measurements in order to see if the tethered balloon design is viable. "If not now, then when would you start?" he asks. "This year, next year? Or maybe wait until a large block of ice falls off of Greenland? My choice is to have all the tools carefully thought through, so that we don't have to rush into anything."
To avoid dangerous climate change, some scientists estimate that global CO2 emissions must be cut by at least 80 percent by the end of the century. Geoengineering will not help achieve that long-term target, but the cooling effects of large sulfate clouds are nearly instantaneous, making geoengineering potentially valuable in the event of acute climate crises such as the melting of Arctic sea ice, which could further accelerate global warming over the decades.
The researchers made it clear in Tuesday's press conference that they do not advocate using geoengineering as an excuse for humanity to continue recklessly emitting carbon dioxide and other greenhouse gases. "[Geoengineering] should be considered as an emergency remediation while we wean ourselves off carbon," Watson said. "The question you have to ask is, is it worse without mitigation or with it? And that answer isn't obvious yet."

Nevertheless, the Canada-based Action Group on Erosion, Technology and Concentration (ETC) is calling the tests internationally irresponsible. In a written statement, they called on the British government to shut down the project, adding: "This experiment is only phase one of a much bigger plan that could have devastating consequences, including large changes in weather patterns such as deadly droughts."
Alan Robock, a Rutgers University meteorologist, shares some of those concerns. He has created computer simulations indicating that sulfate clouds could potentially weaken the Asian and African summer monsoons, reducing rain that irrigates the food crops of billions of people. It is premature to conduct such field experiments, Robock says. More computer modeling should be done first, he adds, to determine how injected particles might interact with the ozone layer and the hydrologic cycle.

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QR Tags Can Be Rigged to Attack Smart Phones

A blogger has demonstrated how these innocuous tags can be made into cyber-crime weapons


You've probably seen QR tags thousands of times, from advertisements in the subway to coupon flyer in the mail to products in the supermarket. They look like stamp-size bar codes, a grid of small black-and-white rectangles and squares, usually with bigger black squares in the corners.
A marketer's dream-come-true, these tiny images are capable of storing and transmitting loads of data directly to the smartphones of interested customers. When a person scans a QR tag with a smartphone, the tag can do any number of things, including taking the user right to the product's website.

                                                    Image: Digitmedia, courtesy Flickr
                                            [How to Protect Your Smartphone From Malware]

But like any technology, they can also be manipulated to bite the hands — or phones — that feed them. On the mobile security blog Kaotico Neutral, researcher Augusto Pereyra demonstrated how these innocuous QR tags can be made into cybercrime weapons.

QR tags are touted for their convenience, but it's that same convenience — coupled with their increasing prevalence — that Pereyra believes could allow them to become dangerous attack vectors. Popular QR tag-scanning software, such as ScanLife, automatically takes mobile browsers to the site embedded within the tag, and while it makes the process quick, it does nothing for its safety.

"This is a serious problem since this is the equivalent of clicking a link with your eyes closed," Pereyra wrote.
Tim Armstrong, researcher for the security firm Kaspersky Lab, said this streamlined process creates a "run first, ask questions later" mentality that benefits attackers.

An attack like his could easily be scaled up, Pereyra said, simply by printing the rigged QR tags and pasting them atop already-existing tags on posters in public places.
As companies and marketers take advantage of the power and ubiquity of mobile devices, and it becomes easier for consumers to carry out financial transactions via smartphones, researchers suspect online attackers will attempt to gain their own foothold in the market.

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August 23, 2011

Ultra-Violet Radiation (UVR) From Tube Light

বর্তমানে একটি জনস্বাস্থ্যমূলক প্রসঙ্গ বারবার উঠে আসছে। তা হল tube light বা fluorescent lamp হতে নির্গত ultraviolet radiation (UVR) শরীরের জন্য ক্ষতিকর কিনা। কারণ UVR হল skin cancer এর জন্য দায়ি, যা মানব স্বাস্থ্যের জন্য হুমকিস্বরূপ। Tube light বা fluorescent lamp হতে নির্গত UVR
নিম্ন চাপীয় mercury বাষ্প হতে উৎপন্ন হয়। যখন electrical discharge mercury বাষ্পের মধ্য দিয়ে চালিত হয় তখন UVR উৎপন্ন হয়অধিকাংশ নির্গত শক্তির wavelength হল 254 nm ইহা UV-C spectrum (180-280 nm) এর মধ্যে অবস্থিত। Fluorescent bulb এর ক্ষেত্রে 254 nm এর  radiation ব্যবহৃত হয় phosphor কে উত্তেজিত করতে, যা bulb এর glass envelope এর ভিতরের দিকে প্রলেপ হিসেবে থাকে। পরবর্তিতে phosphor visible wavelength এর আলো নিঃসরণ করে (বিভিন্ন phosphor বিভিন্ন রঙ সৃষ্টি করে) এবং যে সকল UV-C রশ্নি phosphor শোষণ করে না তা glass wall দ্বারা শোষিত হয়। আবার mercury discharge অন্নান্য wavelength এর যেমন 365 nm এর আলোও নিঃসরণ করে যা UV-A spectrum (315-400 nm) এর মধ্যে অবস্থিত। এই UV-A radiation phosphor দ্বারা শোষিত হয়না এবং অধিকাংশই lamp wall ভেদ করে পরিবেশে মুক্ত হয়।১৯৮৮ সালে NRPB বিস্তারিত গবেষণা চালায় UVR এর উপর। তারা ক্ষতিকর প্রভাব যেমন photokeratitis, erythema ইত্যাদির জন্য মাত্রা  নির্ধারণ করে। এছাড়া non-melanoma skin cancer (NMSC) এর সাথেও UVR এর সংশ্লিষ্টতা দেখানো হয়

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June 22, 2011

Who Is The Father Of Physics?

Physics is the field of science which studies the natural world and the laws on which it works. It is considered as the most fundamental of the sciences from which the other branches like chemistry, biology and application oriented fields like engineering and medicine originate. Physics has been studied by man since ancient times in various ways with a number of eminent personalities contributing a great deal to the field.

Physics though it employs mathematical means to comprehend various concepts which are then subjected to tests or experiments also has a philosophical aspect about it. The ancient Greek philosopher Thales (6th century BC) is widely regarded as the father of physics. He is credited with being the first to study the heavens; some of his achievements include predicting a solar eclipse, construction of an almanac and his statement that all 'things' are formed of one primary element.

Some important philosopher physicists of the period include Aristotle, Democritus and Archimedes. The father of Modern Physics is considered to be the Italian physicist Galileo Galilei most famous for his assertion of the heliocentric view of the solar system.
Some famous physicists of the modern period are Sir Isaac Newton, Johannes Kepler, Benjamin Franklin, Michael Faraday, Nikolai Tesla, Niels Bohr and Albert Einstein among others.
Anonymous

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June 10, 2011

World Health Organization: cell phones possibly carcinogenic

The WHO’s International Agency for Research on Cancer (IARC) previously held that cell phone radiation was not carcinogenic. That partly silenced many critics who claimed cell phone radiation was causing brain tumors and that cell phones were more dangerous than previously believed. It has since upgraded cell phone radiation to the third highest rating, below “probably carcinogenic” and “carcinogenic.”
It’s likely the WHO’s latest classification will once again ignite criticism of cell phones and debate over whether cell phone radiation can cause cancer. There are around 5 billion people currently using cell phones, according to the report by the IARC. The IARC is recommending people take pragmatic measures to reduce exposure to cell phone radiation — such as relying on texting and hands-free communication like bluetooth headsets.
The new classification indicates that there is some link between cancer and radiofrequency electromagnetic fields that are emitted by cell phones, but extensive study is still necessary. The panel found that the evidence that cell phone radiation was linked to one type of brain cancer was “limited” — and the association with any other type of cancer was “inadequate.” According to the report, the “limited” classification is just one step above the “inadequate” classification.
Mobile wireless association CTIA, one of the wireless industry’s main trade groups, refuted the WHO’s findings and said that the panel of scientists did not conduct any new research — instead it just reviewed existing studies. The classification does not mean that cell phones cause cancer and the IRAC has given the same score to other seemingly harmless substances, the association said.
The panel consisted of 31 scientists pulled from 14 different countries that reviewed two large studies that found a relationship between cell phone use and Glioma, a form of brain cancer. The scientists reviewed those studies and other scientific literature for eight days at a meeting in Lyons, France.

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May 06, 2011

X-Rays

APA

National Aeronautics and Space Administration, Science Mission Directorate. (2010). X-Rays. Retrieved March 31, 2011, from Mission:Science website:
http://missionscience.nasa.gov/ems/11_xrays.html

MLA

Science Mission Directorate. "X-Rays" Mission:Science. 2010. National Aeronautics and Space Administration. 31 Mar. 2011 http://missionscience.nasa.gov/ems/11_xrays.html

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May 04, 2011

Visualization: From Energy to Image

APA

National Aeronautics and Space Administration, Science Mission Directorate. (2010). Visualization: From Energy to Image. Retrieved March 31, 2011, from Mission:Science website:
http://missionscience.nasa.gov/ems/04_energytoimage.html

MLA

Science Mission Directorate. "Visualization: From Energy to Image" Mission:Science. 2010. National Aeronautics and Space Administration. 31 Mar. 2011 http://missionscience.nasa.gov/ems/04_energytoimage.html

HOW DO WE VISIUALIZE LIGHT WE CAN'T SEE?

False color, or representative color, is used to help scientists visualize data from wavelengths beyond the visible spectrum. Scientific instruments onboard NASA spacecraft sense regions within the electromagnetic spectrum—spectral bands. The instruments direct the electromagnetic energy onto a detector, where individual photons yield electrons related to the amount of incoming energy. The energy is now in the form of "data," which can be transmitted to Earth and processed into images.

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Infrared Waves

APA

National Aeronautics and Space Administration, Science Mission Directorate. (2010). Infrared Waves. Retrieved March 31, 2011, from Mission:Science website:
http://missionscience.nasa.gov/ems/07_infraredwaves.html


MLA

Science Mission Directorate. "Infrared Waves" Mission:Science. 2010. National Aeronautics and Space Administration. 31 Mar. 2011 http://missionscience.nasa.gov/ems/07_infraredwaves.html


INFRARED ENERGY

A remote control uses light waves just beyond the visible spectrum of light—infrared light waves—to change channels on your TV. This region of the spectrum is divided into near-, mid-, and far-infrared. The region from 8 to 15 microns (µm) is referred to by Earth scientists as thermal infrared since these wavelengths are best for studying the longwave thermal energy radiating from our planet.
A typical television remote control uses infrared energy at a wavelength around 940 nanometers. While you cannot "see" the light emitting from a remote, some digital and cell phone cameras are sensitive to that wavelength of radiation. Try it out!

Infrared lamps heat lamps often emit both visible and infrared energy at wavelengths between 500nm to 3000nm in length. They can be used to heat bathrooms or keep food warm. Heat lamps can also keep small animals and reptiles warm or even to keep eggs warm so they can hatch.

DISCOVERY OF INFRARED

In 1800, William Herschel conducted an experiment measuring the difference in temperature between the colors in the visible spectrum. He placed thermometers within each color of the visible spectrum. The results showed an increase in temperature from blue to red. When he noticed an even warmer temperature measurement just beyond the red end of the visible spectrum, Herschel had discovered infrared light!

THERMAL IMAGING

We can sense some infrared energy as heat. Some objects are so hot they also emit visible light—such as a fire does. Other objects, such as humans, are not as hot and only emit only infrared waves. Our eyes cannot see these infrared waves but instruments that can sense infrared energy—such as night-vision goggles or infrared cameras–allow us to "see" the infrared waves emitting from warm objects such as humans and animals. The temperatures for the images below are in degrees Fahrenheit.

COOL ASTRONOMY

Many objects in the universe are too cool and faint to be detected in visible light but can be detected in the infrared. Scientists are beginning to unlock the mysteries of cooler objects across the universe such as planets, cool stars, nebulae, and many more, by studying the infrared waves they emit.
The Cassini spacecraft captured this image of Saturn's aurora using infrared waves. The aurora is shown in blue, and the underlying clouds are shown in red. These aurorae are unique because they can cover the entire pole, whereas aurorae around Earth and Jupiter are typically confined by magnetic fields to rings surrounding the magnetic poles. The large and variable nature of these aurorae indicates that charged particles streaming in from the Sun are experiencing some type of magnetism above Saturn that was previously unexpected.

SEEING THROUGH DUST

Infrared waves have longer wavelengths than visible light and can pass through dense regions of gas and dust in space with less scattering and absorption. Thus, infrared energy can also reveal objects in the universe that cannot be seen in visible light using optical telescopes. The James Webb Space Telescope (JWST) has three infrared instruments to help study the origins of the universe and the formation of galaxies, stars, and planets.
When we look up at the constellation Orion, we see only the visible light. But NASA's Spitzer space telescope was able to detect nearly 2,300 planet-forming disks in the Orion nebula by sensing the infrared glow of their warm dust. Each disk has the potential to form planets and its own solar system. Credit: Thomas Megeath (Univ. Toledo) et al., JPL, Caltech, NASA
A pillar composed of gas and dust in the Carina Nebula is illuminated by the glow from nearby massive stars shown below in the visible light image from the Hubble Space Telescope. Intense radiation and fast streams of charged particles from these stars are causing new stars to form within the pillar. Most of the new stars cannot be seen in the visible-light image (left) because dense gas clouds block their light. However, when the pillar is viewed using the infrared portion of the spectrum (right), it practically disappears, revealing the baby stars behind the column of gas and dust.

MONITORING THE EARTH

To astrophysicists studying the universe, infrared sources such as planets are relatively cool compared to the energy emitted from hot stars and other celestial objects. Earth scientists study infrared as the thermal emission (or heat) from our planet. As incident solar radiation hits Earth, some of this energy is absorbed by the atmosphere and the surface, thereby warming the planet. This heat is emitted from Earth in the form of infrared radiation. Instruments onboard Earth observing satellites can sense this emitted infrared radiation and use the resulting measurements to study changes in land and sea surface temperatures.
There are other sources of heat on the Earth's surface, such as lava flows and forest fires. The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard the Aqua and Terra satellites uses infrared data to monitor smoke and pinpoint sources of forest fires. This information can be essential to firefighting efforts when fire reconnaissance planes are unable to fly through the thick smoke. Infrared data can also enable scientists to distinguish flaming fires from still-smoldering burn scars.

Credit: Space Science and Engineering Center, University of Wisconsin-Madison, Richard Kohrs, designer
The global image on the right is an infrared image of the Earth taken by the GOES 6 satellite in 1986. A scientist used temperatures to determine which parts of the image were from clouds and which were land and sea. Based on these temperature differences, he colored each separately using 256 colors, giving the image a realistic appearance.
Why use the infrared to image the Earth? While it is easier to distinguish clouds from land in the visible range, there is more detail in the clouds in the infrared. This is great for studying cloud structure. For instance, note that darker clouds are warmer, while lighter clouds are cooler. Southeast of the Galapagos, just west of the coast of South America, there is a place where you can distinctly see multiple layers of clouds, with the warmer clouds at lower altitudes, closer to the ocean that's warming them.
We know, from looking at an infrared image of a cat, that many things emit infrared light. But many things also reflect infrared light, particularly near infrared light. Learn more about
REFLECTED Near-infrared radiation.

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ELECTROMAGNETIC ENERGY

When you tune your radio, watch TV, send a text message, or pop popcorn in a microwave oven, you are using electromagnetic energy. You depend on this energy every hour of every day. Without it, the world you know could not exist.
Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect only a small portion of this spectrum called visible light. A radio detects a different portion of the spectrum, and an x-ray machine uses yet another portion. NASA's scientific instruments use the full range of the electromagnetic spectrum to study the Earth, the solar system, and the universe beyond.

OUR PROTECTIVE ATMOSPHERE

Our Sun is a source of energy across the full spectrum, and its electromagnetic radiation bombards our atmosphere constantly. However, the Earth's atmosphere protects us from exposure to a range of higher energy waves that can be harmful to life. Gamma rays, x-rays, and some ultraviolet waves are "ionizing," meaning these waves have such a high energy that they can knock electrons out of atoms. Exposure to these high-energy waves can alter atoms and molecules and cause damage to cells in organic matter. These changes to cells can sometimes be helpful, as when radiation is used to kill cancer cells, and other times not, as when we get sunburned.

ATMOSPHERIC WINDOWS

Seeing Beyond our Atmosphere

NASA spacecraft, such as RHESSI, provide scientists with a unique vantage point, helping them "see" at higher-energy wavelengths that are blocked by the Earth's protective atmosphere.
Electromagnetic radiation is reflected or absorbed mainly by several gases in the Earth's atmosphere, among the most important being water vapor, carbon dioxide, and ozone. Some radiation, such as visible light, largely passes (is transmitted) through the atmosphere. These regions of the spectrum with wavelengths that can pass through the atmosphere are referred to as "atmospheric windows." Some microwaves can even pass through clouds, which make them the best wavelength for transmitting satellite communication signals.
While our atmosphere is essential to protecting life on Earth and keeping the planet habitable, it is not very helpful when it comes to studying sources of high-energy radiation in space. Instruments have to be positioned above Earth's energy-absorbing atmosphere to "see" higher energy and even some lower energy light sources such as quasars.

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Anatomy of an Electromagnetic Wave

APA

National Aeronautics and Space Administration, Science Mission Directorate. (2010). Anatomy of an Electromagnetic Wave. Retrieved March 31, 2011, from Mission:Science website:
http://missionscience.nasa.gov
/ems/02_anatomy.html

MLA

Science Mission Directorate. "Anatomy of an Electromagnetic Wave" Mission:Science. 2010. National Aeronautics and Space Administration. 31 Mar. 2011
http://missionscience.nasa.gov/ems/02_anatomy.html
Energy, a measure of the ability to do work, comes in many forms and can transform from one type to another. Examples of stored or potential energy include batteries and water behind a dam. Objects in motion are examples of kinetic energy. Charged particles—such as electrons and protons—create electromagnetic fields when they move, and these fields transport the type of energy we call electromagnetic radiation, or light.

WHAT ARE WAVES?
Mechanical waves and electromagnetic waves are two important ways that energy is transported in the world around us. Waves in water and sound waves in air are two examples of mechanical waves. Mechanical waves are caused by a disturbance or vibration in matter, whether solid, gas, liquid, or plasma. Matter that waves are traveling through is called a medium. Water waves are formed by vibrations in a liquid and sound waves are formed by vibrations in a gas (air). These mechanical waves travel through a medium by causing the molecules to bump into each other, like falling dominoes transferring energy from one to the next. Sound waves cannot travel in the vacuum of space because there is no medium to transmit these mechanical waves.
Classical waves transfer energy without transporting matter through the medium. Waves in a pond do not carry the water molecules from place to place; rather the wave's energy travels through the water, leaving the water molecules in place, much like a bug bobbing on top of ripples in water.

ELECTROMAGNETIC WAVES

Credit: Ginger Butcher
Electricity can be static, like the energy that can make your hair stand on end. Magnetism can also be static, as it is in a refrigerator magnet. A changing magnetic field will induce a changing electric field and vice-versa—the two are linked. These changing fields form electromagnetic waves. Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.
In the 1860's and 1870's, a Scottish scientist named James Clerk Maxwell developed a scientific theory to explain electromagnetic waves. He noticed that electrical fields and magnetic fields can couple together to form electromagnetic waves. He summarized this relationship between electricity and magnetism into what are now referred to as "Maxwell's Equations."
Heinrich Hertz, a German physicist, applied Maxwell's theories to the production and reception of radio waves. The unit of frequency of a radio wave -- one cycle per second -- is named the hertz, in honor of Heinrich Hertz.
His experiment with radio waves solved two problems. First, he had demonstrated in the concrete, what Maxwell had only theorized — that the velocity of radio waves was equal to the velocity of light! This proved that radio waves were a form of light! Second, Hertz found out how to make the electric and magnetic fields detach themselves from wires and go free as Maxwell's waves — electromagnetic waves.
Electromagnetic waves are formed by the vibrations of electric and magnetic fields. These fields are perpendicular to one another in the direction the wave is traveling. Once formed, this energy travels at the speed of light until further interaction with matter.

WAVES OR PARTICLES? YES!

Light is made of discrete packets of energy called photons. Photons carry momentum, have no mass, and travel at the speed of light. All light has both particle-like and wave-like properties. How an instrument is designed to sense the light influences which of these properties are observed. An instrument that diffracts light into a spectrum for analysis is an example of observing the wave-like property of light. The particle-like nature of light is observed by detectors used in digital cameras—individual photons liberate electrons that are used for the detection and storage of the image data.

POLARIZATION

One of the physical properties of light is that it can be polarized. Polarization is a measurement of the electromagnetic field's alignment. In the figure above, the electric field (in red) is vertically polarized. Think of a throwing a Frisbee at a picket fence. In one orientation it will pass through, in another it will be rejected. This is similar to how sunglasses are able to eliminate glare by absorbing the polarized portion of the light.

DESCRIBING ELECTROMAGNETIC ENERGY

The terms light, electromagnetic waves, and radiation all refer to the same physical phenomenon: electromagnetic energy. This energy can be described by frequency, wavelength, or energy. All three are related mathematically such that if you know one, you can calculate the other two. Radio and microwaves are usually described in terms of frequency (Hertz), infrared and visible light in terms of wavelength (meters), and x-rays and gamma rays in terms of energy (electron volts). This is a scientific convention that allows the convenient use of units that have numbers that are neither too large nor too small.

FREQUENCY

The number of crests that pass a given point within one second is described as the frequency of the wave. One wave—or cycle—per second is called a Hertz (Hz), after Heinrich Hertz who established the existence of radio waves. A wave with two cycles that pass a point in one second has a frequency of 2 Hz.

WAVELENGTH

Electromagnetic waves have crests and troughs similar to those of ocean waves. The distance between crests is the wavelength. The shortest wavelengths are just fractions of the size of an atom, while the longest wavelengths scientists currently study can be larger than the diameter of our planet!

ENERGY

An electromagnetic wave can also be described in terms of its energy—in units of measure called electron volts (eV). An electron volt is the amount of kinetic energy needed to move an electron through one volt potential. Moving along the spectrum from long to short wavelengths, energy increases as the wavelength shortens. Consider a jump rope with its ends being pulled up and down. More energy is needed to make the rope have more waves.





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