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--------------------- 2661 - LIGHT - What It Means To Be Visible?
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- Electromagnetic radiation and gravity are the only two ways we know of to communicate “information“. Both are carried by massless particles, or waves, known as photons and gravitons. Because they are massless they MUST always travel at the constant speed of light.
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- The maximum speed that information can travel is the speed of light. You can not learn anything any faster than that.
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- Electromagnetic radiation and information come to us, and to our eyes, in very small bundles of energy. The energy of each photon of light is E = h*f. The photon energy, “E“, is directly proportional to the frequency of oscillation ,”f”, of the electric wave and the magnetic wave that are oscillating together. “h” is a constant for the units we use to measure the action of the energy.
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- In our case “h” = the constant 6.7 * 10^-11. This constant is know as Planck’s Constant of Action.
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-------------------- E = h * f
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-------------------- Photon Energy = 0.000,000,000,067 * frequency
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-------------------- Photon Energy = kilograms * meters^2 / seconds^2
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---------------------Photon Energy = joules, which is the name given to kg*m^2/sec^2
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- These units for energy should look familiar to you. Remember, E=m*c^2. Energy is directly proportional to mass. In this case the constant of proportionality is the speed of light squared. “c^2” = 9*10^16.
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-------------------- E = c^2 * m
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-------------------- Mass Energy = 90,000,000,000,000,000 * mass
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-------------------- Mass Energy = kilograms * meters^2 / seconds^2, or joules
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- The “h” Constant of Action is a very small number for a single photon. The “c^2” number is a very large number for a kilogram of mass converted into energy. However, the electromagnetic energy of the photon is directly proportional to the frequency of oscillation. And, electromagnetic energy spectrum of oscillations covers a wide range of frequencies from radio waves, to light waves, to X-rays and Gamma Rays.
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- The low energy radio frequency waves have oscillations in the order of 1000 cycles per second. (kilohertz).
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--------------------- Energy of radio wave = 6.7*10^-11 * 1000
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--------------------- Energy of radio wave = 6.7*10^-8
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--------------------- Energy of radio wave = 0.000000067 joules.
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- At the other end of the spectrum, the high energy Gamma Ray frequency waves have oscillations in the order of 10^24 cycles per second. (femtohertz).
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--------------------- Energy of Gamma Ray = 6.7*10^-11 * 10^24
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--------------------- Energy of Gamma Ray = 6.7*10^13
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--------------------- Energy of Gamma Ray = 6,700,000,000,000 joules.
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- As you can see the electromagnetic spectrum covers a wide range of energies.
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- For the energy of light that our eyes can see we are limited to a spectrum of wavelengths from 400 nanometers blue light to 750 nanometers red light.
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- Above and below these wavelengths lies ultraviolet and infrared that our eyes can not quite visualize. 400 and 750 nanometers wavelengths correspond to frequency of oscillations of 750*10^16 cycles per second for blue light and 0.04 * 10^16 cycles per second for red light.
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----------------------------- frequency * wave length = the speed of light
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------------------------------------------- f * w = c
--------------------- Energy of blue light = 6.7*10^-11 * 750*10^16
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--------------------- Energy of blue light = 5 * 10^8 joules
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--------------------- Energy of blue light = 500,000,000 joules.
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--------------------- Energy of red light = 6.7*10^-11 * 0.04*10^16
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--------------------- Energy of red light = 0.26 * 10^8 joules
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--------------------- Energy of red light = 25,600 joules
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- Blue light has a lot more energy than red light. That is the reason infrared makes you feel warm, but violet and ultraviolet light give you a sunburn.
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- Our eyes are amazing instruments in their ability to detect over a range of 20,000 magnitudes of energy levels. Some human eyes can detect a single photon of light. Most can detect a level of energy of 4 to 5 photons of light.
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- Things are visible because electromagnetic energy reaches our eyes. But, what causes electromagnetic energy? In a word, “atoms“. Light is the oscillation of electric waves and magnetic waves traveling together at the speed of light.
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- A magnetic wave, or a magnetic field, is created when an electric charge is in motion. An electric field is created when a magnetic field is in motion. Each one creates the other when they are moving through space. And, the two waves moving together can only move at one constant speed.
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- The simplest atom is hydrogen, that is made up of a single positive charge proton at the nucleus and a single negative charge electron orbiting around it. All atoms are little magnets because the electric charge of the electron is in motion around the nucleus.
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- Motion is not only linear, it is circular as well. And, circular motion requires acceleration. A force is not needed to keep an object in motion at a constant velocity in a straight line.
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- However, if an object’s velocity is going in a circle its velocity is constantly changing, because the direction is changing. A force is required to accelerate a mass. And, acceleration is the same as a changing velocity, so a force is required according to Force = mass * acceleration, F = ma.
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- The mass times velocity is called angular momentum. Electrons are always spinning in an atom as well as orbiting. Therefore, electrons always have angular momentum. A spinning electron always maintains its own magnetic field resulting from their negative charge being in motion.
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- Electrons can only spin in one of two ways, clockwise, or flip them over and they can spin counter-clockwise. So, the magnetic field’s poles north and south can only point in the direction of the spin axis of the electrons up spin or down spin. If we line up a lot of electrons in a metal all pointing in the same spin axis direction we create a permanent magnetic.
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- As long as the atom is experiencing constant acceleration, in other words its changing velocity remains the same, then the atom does not emit any photons.
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- However, if there is a force causing the atom to accelerate its motion, or the electrons to jump to lower levels of orbit, than photons can be emitted. Thermal energy is the most common way the motion of atoms can speed up. Faster jittering under increasing heat causes acceleration increases causing photon energy to be radiated out of the atoms.
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- A force is needed to cause an atom to accelerate. F = m*a. Energy is defined as a force acting over a distance. E = F*d. Therefore, Energy = m*a*d. Electromagnetic Energy is radiated whenever a charged particle, like the electron, increases its acceleration of motion, “a“.
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- Electromagnetic Energy is also radiated when the electron jumps some distance, “d”, between orbits, which are at specific energy levels inside each specific atom. Each atomic element in the Periodic Table has its own unique structure of electrons and energy levels orbiting the nucleus.
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- When photons are emitted, or absorbed, by each atomic element a different frequency arrangement is created, depending on these unique energy levels. Again, this is according to Energy = 6.7*10^-11 * frequency. So, if astronomers measure the frequencies in the light spectrum coming from the stars they can identify what elements are there or in the interstellar gas in between. This study is called “spectroscopy“.
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- Everything that is visible is either creating electromagnetic energy in its atomic structure or it is reflecting some of this electromagnetic that is coming from another atomic structure source.
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- Our biggest source for photons is the Sun. But, anytime atoms gain energy through increased acceleration or loose energy when electrons drop to lower energy levels, photons are created. Atoms absorbing photons gain energy by moving electrons to higher energy levels. Atoms can absorb and emit photons only at the energy levels, and frequencies, permitted by their own unique atomic structure.
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- All other photons are reflected. That is why everything has a different color. What is not absorbed is reflected. What is reflected is the color you see. Color is just another name for frequency. Frequency is just another name for electromagnetic energy.
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- All electric fields and magnetic fields are defined from an electric charge being in motion. All motion is a change of space per change in time.
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- What makes things visible is a combination of all of these creations the natural world has given us. Just because something is clearly visible doesn’t mean it is understood. I hope my review helped your understanding a little.
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- March 10, 2020 2661
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--------------------- Tuesday, March 10, 2020 --------------------
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