Friday, January 06, 2006

Electromagentism

If you grew up in the seventies you probably remember School House Rock, a Saturday Morning filler between shows that tried to teach us school subjects with groovy music and illustrations. One of the little ditties was called “Electricity!” It went a little something like this:

Music & Lyrics: Bob Dorough
Sung by: Zachary Sanders
Animation: Kim & Gifford Productions

When you're in the dark,
And you want to see
You need uh...

Chorus: Electricity, Electricity!

Flip that switch
And what do you get?
You get uh...

Chorus: Electricity, Electricity!

Every room
Can now be lit
With just uh...

Chorus: Electricity, Electricity!

Where do you think
It all comes from?
This powerful...

Chorus: Electricity, Electricity!

Without electricity the world would not work. I don’t just mean your iPod and laptop will not work, I mean literally, the universe, as we know it would not work. Not just electricity but electromagnetism, the force that just about every experience you have everyday of your life depends on. That electromagnetism is an important a force in the universe is an understatement. If you hit a homerun, it’s because of electromagnetism. If your cells reproduce it is because of electromagnetism, if you have a scotch on the rocks, it’s because of electromagnetism. Really.

Everything in the universe is made of small atomic constituents: electrons, neutrons and protons. Electrons are negatively charged, Protons are positively charged and Neutrons have no charge. Thus everything in the universe, built from atoms is dependant on the electric charge of electrons and protons.

If an atom is charged it is called ionized. That means it has less electrons than protons. In that case it looks to share electrons with other atoms. These combine and become stable again but they form different molecules that make up the stuff of the universe. When they combine and become stable they once again resist being combined with other molecules. Most molecules are a combination of atoms that have a net neutral charge. They are locked together because of their shape in a solid and just bouncing off each other in a liquid. In a gas they are sparsely connected and moving quickly.

So when you hit a ball with a bat, the ball bounces off the bat and over the fence for a homerun. Molecules are happy to be molecules and when they are already sharing electrons and the energy level is not extremely high they tend to stay pretty static if they are inert. Wood and leather are inert. When you have two unstable materials like Chlorine and Sodium and they combine, you release a lot of energy but in the end you have very inert matter, salt. When Chlorine and Sodium come in contact one of the Sodium electrons is lost to a Chlorine atom. In that process energy (photons) is released.

So to have a negative charge is to have a surplus of electrons. To have a positive charge, there are more protons than electrons. In reality the way it works is that the atom has a lack of electrons. The number of protons in an atom determines what element it is. For example: Hydrogen has one proton and one electron. If it has no electrons it is a Hydrogen Ion.

The Greeks discovered that by rubbing fur on amber they could cause sparks. Or they could attract light material, like hair. That spark is the same phenomenon that causes a shock when you walk across the carpet and touch your little sister. What? You never did that? That’s called Static Electricity. What you are actually doing is building up the number of electrons in your body (or possibly vice-versa.) You become negatively charged by accumulating electrons from the rug. You are negatively charged! Your little sister while sitting there not moving is not building up any extra electrons so she is not charged. By touching her you share your imbalance of charge and you zap the hell out of her.

As a fundamental force, Electromagnetism is pretty, uhh… fundamental. Something so fundamental and basic is sometimes very hard to grasp. Because electromagnetism is involved with just about every process known to mankind, it’s complicated and it’s effects, pervasive. Electromagnetism encompasses the electric field and magnetic field, which are like two heads of the same coin or a double-edged sword.

The Electromagnetic field is the force that is produced by an exchange of photons between charged particles from a positively charged particle to a negatively charged particle. If a positively charged particle and a negatively charge particle come in the vicinity of each other they pass photons back and forth between each other like two ball player playing catch. As they get closer the throw the photon ball quicker and the force becomes stronger and stronger until they come in contact. The photon is the force carrier particle in electromagnetism. Like with all the fundamental forces, a particle carries the force. We have discovered the carrier particle in every force except gravity where that force’s particle, a graviton, is still theoretical.

Now, it’s a hard thing to imagine, two particles, exchanging a smaller particle creating the force that is essential to all processes in the universe, but that’s the way it is. As a part of Quantum Mechanical theory, all forces come in packets or quanta. (Hence Quantum.) But as one of the strange and almost unfathomable aspects of this theory is that those same particles also behave like waves. In experiments with light and electrons those particles, very much smaller than we can imagine, both produce wave-like and point-like effects on experiments.

Light as a Wave

Light can be measured as a wave when we conduct an experiment involving tiny slits and a light sensitive plate behind those slits. When both slits are opened and a light source is shined through, an interference pattern of overlapping radiating circles burns on the plate. A sure sign that a wave is present. Think of the way a wave looks with its highs and lows. When two waves intersect, where the waves are at the top or crest the result is a doubling of their strength. When two waves intersect at the bottom of their strength or trough, the two become lower by double. This effect is seen in both Quantum Physics and ocean waves. When two waves converge, one at the crest and one at its trough they cancel each other out. The effect of this is the interference pattern.

In the same double-slit experiment if we close on of the slits and then shine the light through it, then turn off the light source and then alternate opening from one side and then another we would expect that the light pattern would simply grow behind each slit and not interfere with each other. We can guess this because, when the light is shining through one slit the wave from the other slit is cut off—because the other slit is closed—so there is no interference of the waves. This would produce two distinct glows behind the slits. Wrong!




Thomas Young, a physician and physicist from the 1800s invented this experiment to prove his theory that light propagates as a wave. It supported his theory and other theories he had about the wave like nature of light including how it separates into wavelengths of color which he observed as light passed through a thin film, like soap bubbles, creating a colorful band—think rainbow. Everyone knows that a rainbow splits the light in sunlight into the basic colors remembered by the infamous Roy G. Biv. That’s how my elementary school teacher taught us the colors of visible light: Red Orange Yellow Green Blue Indigo Violet. Or the acronym, Roy G. Biv, maker of rainbows!


In that spectrum are the ingredients and secret to every color you see. A color is simply the reflection back to your eyes a certain color spectrum of the visible light spectrum. Red ink reflects the red wavelength, Green, the green wavelength. The answer to the age-old question of why the sky is blue is that the atmosphere scatters the blue light spectrum waves of sunlight. It’s also because if the sky were green you’d never know where to stop mowing your lawn!

What do Doctors, Jackson Pollack, sunburns and the song “My Heart Will Go On” have to do with each other? I know that you’re saying to yourself that you can make some connection with Doctors, Jackson Pollack and sunburns but… Celine Dion? What does Celine Dion have to do with Electromagnetism? Everything! See, the radio waves that come to your car radio from the Easy Listening station are very long, weak energy waves of the electromagnetic spectrum.



Looking at this chart from the NASA website, you see where things fall on the spectrum and the length of the wavelength. Visible light, all the colors found in the Abstract Expressionist paintings of Jackson Pollack are located on a narrow part of the scale. Ultraviolet light, shorter wavelength radiation on the EM scale, causes sunburns. Our eyes are sensitive to the visible light spectrum and coincidentally this is the range that the sun emits most of its radiation in. The sun also emits a lot of ultraviolet radiation but most of that is absorbed by the earth ozone layer. If not for that layer, the earth would be a scorched desert. Not a pleasant place but because of the delicate balance of nature we are protected from most of the suns harmful rays and mostly the less harmful visible light falls on us. Beachgoers worship the UV wavelength of electromagnetism but I doubt they’d want to live on a planet without an ozone layer. This is why we place so much importance on not eating up that layer with ozone destroying chemicals.

Ever had an X-Ray? Well they are machines that transmit high-energy, small-wavelength radiation waves through your body. The softer tissue in your body doesn’t stop the waves but the bones do a little so the image left on a X-Ray sensitive plate is where the X-Rays were stopped by the bones producing a negative image where the X-rays that come through burn onto the plate outlining the bones. Because the X-Rays are so high energy they are dangerous and it’s not recommended that you hang out inside X-Ray machines unless prescribed by a doctor.

Gamma Rays are very high frequency waves that are dangerous to humans, basically all life in general. I am still trying to figure out how Bruce Banner became the Incredible Hulk by exposing himself to Gamma Rays. I expect that he would have fried his body with that type of experiment not morphed into a huge mean and green, but lovable monster with bad grammar.

Gamma Rays are produced in very high-energy situations like say when a Black Hole is consuming a Neutron Star. Not something you’re going to see on your commute home from work, hopefully. But it is something we can observe by looking at the radiation of material sped up to the speed of light as it approaches consumption in a Back Hole. This heats the material of the star causing it to radiate in the Gamma Ray spectrum, which is, if you remember your EM scale, very high energy. The Neutron star comes close enough to a Back Hole for it to begin circling it. The irresistible gravity of the Back Hole sucks the Neutron Star closer. The Neutron Star gets hot. It starts to fall to pieces under the attraction of the Black Hole. It gets really hot and rotates faster and faster until it flies apart and joins the Black Hole. At the end, the Black Hole becomes enlarged and then ejects a short Gamma Ray Burst signaling the end of the orgasmic dance between Neutron Star and Black Hole. Here is a little movie of that happening in case you like to watch. Usually, after this event there is an X-Ray glow as the Black Hole, like a hungry predator, devours the remnants of the material. If you think that’s cool check out this movie of two Neutron Stars colliding.

NASA is a cool place, ain’t it?

The strength of a wave depends on the height of the wave. This is called its intensity, like bright light, the kind Gremlins really hate. The brighter the light, the higher its wavelength. The height and depth of a wave is called amplitude. Think of a wavy line where the waves are all the same size and length. Then draw a line at the midsection of the wave lengthwise. If you measure the distance between the line (also called the traverse and the top (or crest) of the curve, that is its amplitude. To be more exact, that is its positive amplitude. If you measure the distance between the traverse and the lowest point on the curve of the wave or the trough that is called its negative amplitude. This is how electromagnetic waves are measured, by the wave length or the distance from crests and crest (which determines the type of radiation) and the distance between the traverse and the crests and troughs which is the intensity or frequency which is how many waves pass a certain point in a certain amount of time, usually cycles per second. One wave passing per second is one cycle per second. A cycle per second is also called a Hertz. 100 Hertz is 100 cycles per second. In a vacuum, Electromagnetic waves travel at the speed of light, which is denoted by c.

On the other hand, or on the other side of the coin or on the other field of the electromagnetic spectrum, as the cool folks say, photons—the carrier of electromagnetic force—act like particles.

In his book Opticks, published in 1704, Isaac Newton proposed his theory that light was made of corpuscles. He came to this idea by observing reflection and refraction of light. He deduced that light corpuscles had repulsive and attractive forces which fit perfectly with his laws of motion. The idea was inventive but full of holes, like the concept of diffraction. This is when a wave spreads out in multiple directions when it meets and object. The most obvious example of this is the interference pattern. The corpuscular idea prevailed until the early 19th century when it was replaced by the wave theory. In Quantum Physics the particle and wave theories are combined in the wave-particle duality. It must be noted that the particles of modern Quantum Physics bear little resemblance to Newton’s corpuscles.

Max Planck when thinking about the radiation coming from a body related to temperature led to him theorizing that the vibrating energy of atoms has to be quantized to make the data work. The constant that related energy to frequency of vibration became a small number known as Planck’s Constant.

Though the constant was extremely small it nevertheless was quantized number representing the smallest measurement possible. Nothing could then be smaller than that constant without destroying the mathematics established. This constant has been used in everything from the quantum theory to the smallest size that we can measure the universe at the time of the big bang. It’s like a fundamental measurement of the universe like the speed of light. It represents a universal limit on the physical makeup of the universe. This is shown in a very simple but elegant formula: E=hf. Where E is Energy, h=Planck’s Constant (h = 6.626069 x 10^-34 Joule seconds) and f is the frequency.

Albert Einstein took that information and theorized that light comes in quantized packets called photons that are as small as Planck’s Constant and made of pure energy. Thus, Quantum Physics was born. Planck’s Constant is the smallest fundamental limit in scale for space-time that occurs near 10^-33 centimeters and 10^-43 seconds. Translated this means that Planck observed that reality, the universe, spacetime continuum, whatever you want to call it has a smallest measurement in both distance and time. Nothing is smaller than these measurements and nothing in time can happen in less time. The universe is built from these packets or quanta. (And as I mentioned previously, this is where the term Quantum Physics comes from.) The basic structure of the universe is a mosaic of Planck sized chucks of distance and time.

Einstein used the details of the photoelectric effect to prove that light comes in particles, packets or quanta. The intensity or amplitude of the wave should be the only factor that knocks electrons off a metal. In the photoelectric effect, frequency of the light wave causes more particles to be knocked off but at the same speed as low frequency waves because the intensity of the energy hasn’t changed. Confused. Me too.

Think of how the world is constructed, of small vibrating atoms with electrons surrounding a nucleus of neutrons and protons. The metal is like a huge structure made of these little energy “balls”. The light is shot at the structure of energy balls and if the intensity (or strength) of the light is great enough it will knock the balls of electrons off the structure when they hit. Since we know photons (the balls that make up light) “thrown” at the metal structure come at a certain intensity they will knock off the balls only when that intensity is at a certain level. Then we see one electron being knocked off at a time. When we throw more balls of photons at the balls of the metal structure we knock them off more often but when they come loose they come off at the same speed because the frequency is higher but the strength is the same.

If we lower both the frequency and intensity then fewer balls come off at lower speeds. If we increase the intensity then balls come off at a higher speed. If we increase the frequency then the balls come off more often. This is the Photoelectric Effect. Einstein won his Nobel Prize in 1921 for his work on the Photoelectric Effect not for his Theories of Relativity.

Thus we have two competing descriptions of energy: particle and waveform. This is known as the wave-particle duality. This is actually one of the more mundane paradoxes of quantum physics, believe it or not. To see the photoelectric effect and play with a cool little program that shows how this works go to this page...

Next... The M in EM...

2 comments:

The Phoenix said...

Funny how it all comes back to quantum physics.

ObilonKenobi said...

Yes. It is...