Electric charges have virtual photons streaming outward as straight lines in all directions, making electric field. Electric fields begin at electron edge, which emits virtual photons. Electric-field lines indicate electric-force direction. Each line is one photon stream, so electric-field lines are not about electric-force strength or electric-field strength. Electric-field-line area density, photons per area, is electric-field strength. Because area varies directly with squared dimension, electric force decreases as distance squared: 1/r^2. Electric field has virtual kinetic energy, which can transfer to other charges at field positions to become potential energy.
moving charges
Maximum charge velocity is typically one-tenth light speed. For constant-velocity charge, electric field moves at same speed and direction as charge. Virtual photons stream outward as straight lines in all directions.
Constant-velocity fields have no transverse or longitudinal field changes, and so no waves.
moving charges: magnetic force
According to special relativity, constant-velocity charge causes observer transverse to charge-motion-direction to see length contraction and so increased charge-motion-direction charge density. Length contraction makes flattened-spheroid charge shape, with short axis in motion direction and long axes in transverse-direction plane. Because total charge is same for moving and stationary charge, total field strength stays the same. Relativistically increased charge density along vertical direction causes increased electric force along horizontal direction. Therefore, relativistic length contraction makes electric field appear to observer stronger horizontally. According to special relativity, observer in front or back of constant-velocity charge does not see length contraction, only that charge approaching or receding. Total electric field strength is same as for stationary electron, because total charge is same. Because total charge is same as before, charge density must be less as observed from vertical direction, so electric field appears to observer weaker vertically. Vertical electric field is foreshortened in motion direction, because electron catches up to virtual photons. Vertical electric field is lengthened opposite to motion direction, because electron moves away from virtual photons.
Electric force due to relativistic length contraction and charge-density change, and not due to total charge, is magnetic force. (Stationary charges have no relativistic motion and so no relativistic electric force.) Adjacent magnetic force is a torus around moving charge. Just as electric forces act only on electric forces, magnetic forces act only on magnetic forces, because magnetic is perpendicular to electric and so does not affect electric.
Electric force has electric field. Electric force and electric field have same direction and relative strength. Because magnetic force is relativistic electric force, magnetic force has magnetic field. Magnetic force and magnetic field have same relative strength but perpendicular direction, because force is due to transverse relativistic length contraction and so is perpendicular to motion and field. Therefore, magnetic forces have magnetic fields perpendicular to electric force/magnetic force and perpendicular to charge-motion orientation. Moving-charge magnetic field is a torus adjacent to and around charge, transverse to motion direction. See Figure 1.
For positive charge moving in right-hand thumb direction, magnetic field is in curling index-finger direction, in a circle around moving proton, and magnetic force is outward from palm (right-hand rule). For proton moving vertically downward, magnetic field is in on left and out on right. Electron has negative charge, so magnetic field is out on left and in on right.
Magnetic field has virtual photons and so has virtual kinetic energy, which can transfer to other charges at field positions to become potential energy. Stationary charge has no magnetic field, because it has no relativistic length contraction.
accelerating charge
Charge acceleration pushes electric-field line transversely and stretches it sideways, causing tension and restoring force. Charge acceleration causes transverse electric field, while keeping radial field. Because virtual photons continually leave charge, transverse component moves outward along field line, so spatial transverse waves travel outward. See Figure 2.
Charge acceleration pushes magnetic-field line transversely and stretches it sideways, causing tension and restoring force. Charge acceleration causes magnetic field in charge-motion direction, transverse to magnetic field.
When stationary charge accelerates to constant velocity, electric-field lines curve toward motion direction, because charge and adjacent photon have higher velocity. When constant-velocity charge decelerates to zero velocity, electric-field lines curve away from motion direction, because charge and adjacent photon have lower velocity.
See Figure 3. Force causing electron deceleration also puts transverse upward pushing force on field lines and distorts electric-field lines. As electron slows down, electric-field-lines beginning at electron edge slow down, so horizontal electric-field lines begin to have transverse component upward.
See Figure 3. As electron slows down, electric-field upward transverse component increases over time. Changing electric-field flux (changing electric force) through an area causes relativistic length contraction transverse to area (in same plane) and magnetic-force change in toward or out from area (in same plane), and so causes induced magnetic field around area. Magnetic force has gradient in or out and so makes induced-magnetic-field gradient around. Faster change makes larger gradient.
Electric and magnetic fields interact, so they push/pull adjacent electric and magnetic fields. Interaction is strong and happens at light speed, so adjacency effect travels at light speed. Interaction is constant, so light speed is constant. All interactions are elastic, with no losses to heat or other energy, so induction has same effect later as at beginning.
Transverse effect travels inward and outward at light speed. Outward effect sees only undisturbed field line and so is the only effect and carries energy outward. Inward effect sees restoring force from stretched field line and so forces cancel and line returns to equilibrium, with no energy carried.
Electric-field increase (or decrease) causes magnetic-field increase (or decrease) that opposes electric-field increase (or decrease), by energy conservation.
See Figure 3. Induced magnetic field increases over time. Changing magnetic-field flux (perpendicularly changing magnetic force) through an area causes relativistic length contraction transverse to area (in same plane) and electric-force change around area (in same plane), and so causes induced electric field around area. Electric force has gradient in or out and so makes induced-electric-field gradient in or out. Faster change makes larger gradient.
Magnetic-field increase (or decrease) causes electric-field increase (or decrease) that opposes magnetic-field increase (or decrease), by energy conservation.
Changing electric field and magnetic field are in phase, because they both increase together and both gradients are in same direction.
Gradient and wave leading edge travels outward at constant light speed.
See Figure 3. Horizontal electric-field lines continue moving at constant velocity, because lines have same momentum, inertia, and kinetic energy as before.
See Figure 4. As electron slows down more, electric-field-line points at electron edge slow down more, so horizontal electric-field lines have greater transverse component. Electric-field upward transverse component increases more over time and so makes bigger induced-magnetic-field gradient. Induced magnetic field increases more over time and so makes bigger induced-electric-field gradient. Transverse fields have potential energy, so horizontal electric-field lines at transverse fields have less kinetic energy. Horizontal electric-field lines continue moving at constant velocity, because lines have same momentum, inertia, and kinetic energy as before.
See Figure 5. Metal plate stops electron within one electron width, so distance and time are small, and deceleration is high. Electron is at zero velocity, so current is zero. Electron has no kinetic energy and momentum. Original electric field is symmetric. Original electric field has same potential energy. Original magnetic field is zero. Original magnetic field has no potential energy.
See Figure 5. As electron stops, electric-field-line ends stop, so horizontal electric-field lines have maximum transverse component. As electron stops, electric-field upward transverse component has increased to maximum over time and so makes induced-magnetic-field gradient. Induced magnetic field has increased to maximum over time and so makes induced-electric-field gradient. Induced electric field is maximum.
See Figure 5. Horizontal electric-field lines continue moving at constant velocity, because lines have momentum, inertia, and kinetic energy.
See Figure 6. Deceleration has stopped, so electron and adjacent fields stop feeling upward force. Transverse electric-field stays constant at zero, and so makes no magnetic-field gradient and no magnetic field. Magnetic-field line feels no force, so transverse magnetic field stays constant at zero, and so makes no electric-field gradient and no electric field. Electron and adjacent electric-field line have no velocity, momentum, or kinetic energy. Gradient and wave leading edge travels outward at constant light speed. Adjacent virtual photon leaves electron and travels horizontally at light speed. Transverse electric-field-line component stretches farther downward. Transverse electric-field-line component moves outward at light speed. All interactions are elastic, with no losses to heat or other energy, so gradient has same effect later as at beginning. Original virtual photons of horizontal electric-field lines continue moving at constant velocity, because lines have momentum, inertia, and kinetic energy.
phase
When stationary charge accelerates to constant velocity, electric-field and magnetic-field transverse component increase in same direction and at same time (in phase). When constant-velocity charge decelerates to zero velocity, electric-field and magnetic-field transverse component decrease in same direction and at same time (in phase).
induction
Electric-field change over time (flux) through an area makes magnetic field around area, because of relativistic length contraction. Electric current makes magnetic-field torus around current. See Figure 1.
Magnetic-field change over time (flux) through an area makes electric field around area, because of relativistic length contraction. Magnetic-field flux change through torus cross-section makes electric field around torus cross-section. Current goes through torus hole, around, and back again to complete the circuit (displacement current). See Figure 1.
Stationary electric field has constant force, and so uses no energy to make magnetic field. Moving electric field changes over time and makes constant magnetic-field gradient, because electric-field-movement kinetic energy increases magnetic-field potential-energy over space. Accelerating electric field makes increasing magnetic-field gradient, because electric-field force increases magnetic-field acceleration over space. Accelerating magnetic or electric fields over space have force that causes increasing electric or magnetic fields over time. Fields over space have potential energy, and fields over time have kinetic energy, so energy alternates between kinetic and potential, making waves.
Constant stationary magnetic field has no affect, because it has no force, so magnetic-field energy remains potential energy. Moving magnetic field changes over time and makes constant electric-field gradient, because magnetic-field-movement kinetic energy increases electric-field potential-energy over space. Accelerating magnetic field makes increasing electric-field gradient, because magnetic-field force increases electric-field acceleration over space.
induction: energy conservation
Increasing (or decreasing) magnetic field increases (or decreases) electric field, which makes magnetic field that opposes original magnetic field, by energy conservation. Decreasing (or increasing) electric field decreases (or increases) magnetic field, which makes electric field that opposes original electric field, by energy conservation.
For downward current, acceleration increases magnetic field, and that makes upward electric field, which decreases magnetic field. For downward current, deceleration decreases magnetic field, and that makes downward electric field, which increases magnetic field.
Charge deceleration is against restoring force and builds potential energy. When deceleration stops, restoring force pulls back toward equilibrium, but potential energy transfers to kinetic energy and carries past equilibrium until restoring force pulls back to equilibrium.
Energy goes into adjacent electric-field transverse movement, as interchange between electric and magnetic fields makes wave travel outward. Therefore, energy dies down at past points.
Magnetic-field and electric-field changes have same displacement amount, but electric field has approximately one hundred times more energy. Most light-wave energy is in electric field, not magnetic field, because magnetism is relativistic effect.
To make electric field, virtual photons stream outward at light speed from electron in all directions. Electric-field lines are virtual photon streams. At electron constant velocity, photons also have same velocity as electron, so electric-field lines are straight.
The figure shows virtual photons streaming outward horizontally from electron transverse to electron motion direction. Electron and electric-field lines move downward at same velocity.
Because electric-field and magnetic field interact along line, line has tension, just as a taut string has tension, so line has restoring force if accelerated sideways, just like a taut string has restoring force. All interactions are elastic, with no heat losses, so forces and energies are the same all along electric-field lines from beginning to infinity.
Deceleration can knock field lines through space. Stronger deceleration makes farther and stronger fields.
gradient
Field induction around area circumference makes space gradients as tangents to circumferences. When electric-field flux change through area makes magnetic field around area, magnetic field has gradient around area. When magnetic-field flux change through area makes electric field around area, electric field has gradient around area.
speed
Because electric force is strong, electric and magnetic fields interact at light speed. Because magnetic field and electric field couple {electromagnetic wave induction}|, transverse field-line component moves outward along electric-field line at light speed. Electromagnetic interaction strength is constant, so light speed is constant.
wave
Waves are local effects that travel. Traveling field changes are independent of original charges.
For downward current, deceleration decreases magnetic field, and that makes downward electric field, which increases magnetic field. Electric and magnetic fields are in phase. Electric-field-line disturbance moves away from charge at light speed in a straight line. Transverse component makes traveling wave half {half-wave, wave}. All disturbances to electric-field lines travel outward at light speed. Previous points have no more disturbances, so only one half-wave exists at any time. No disturbances are left behind, because all energy has traveled away. Disturbance reaches farther positions in sequence out to infinity. See Figure 1 through Figure 7. Wave exists only at induction point and can only go straight-ahead. Wave has no physical effect except at moving single point.
elastic
Electric and magnetic interactions are elastic, with no losses to heat or other energies. Therefore, disturbances travel without losing energy. Inductions continue to infinity.
strength with distance
Inductions and other electric-field-line disturbances are transverse to electric-field lines. Because electric field oscillates in a plane, not area, intensity decreases directly with distance, not with distance squared. Transverse effects happen in one dimension, so wave strength decreases directly with distance: 1/r. At later times, transverse field component stretches more over space.
electric-field-line tension and restoring force
Guitar-string molecules attract each other by electric forces. Taut guitar strings have tension from these restraining forces. Pulling string sideways puts potential energy into the string, by stretching string electric forces, like springs. After releasing string, electric forces, like springs, pull string back by restoring force. Potential energy transfers to kinetic energy. Molecule kinetic energy carries molecules past equilibrium point, so they pull on string molecules in other direction.
Adjacent to pull and release point, molecule electric forces pull-and-restore adjacent string molecules, so transverse waves travel along string. Wave speed depends on molecule electric-force strength. Wave takes energy with it, so no energy is left at original disturbance point, and it no longer oscillates. Molecule electric forces bring displacement back to equilibrium at zero.
Electric-field lines are like strings. Like guitar strings, electric-field lines have tension, because electric fields couple to adjacent magnetic fields, and magnetic fields couple to adjacent electric fields. Electric-field and magnetic-field inductions cause adjacent electric-field line points to attract, like molecule electric forces. Pushing electric-field line sideways adds potential energy. Electric-field and magnetic-field inductions make restoring force that transfers potential to kinetic energy.
Electric-field-line-point transverse disturbance displaces adjacent points, which displace their adjacent points, so disturbance travels outward along electric-field line. Electromagnetic interactions are at light speed, so wave has light speed. Wave takes energy with it, so no energy is left at original disturbance point, and it no longer oscillates. After disturbance, electric-field and magnetic-field mutual-induction restoring force brings displacement back to equilibrium at zero.
metal plate
Plate-molecule electric force decelerates electron and so decelerates electric-field line and magnetic-field line at electron edge, transverse to motion direction.
electric and magnetic forces
When electric-field-line disturbance reaches test charges far away from original charge, test charges move along charge-motion direction, because transverse electric field is voltage and electromotive force. Electric-field change and magnetic-field change reach test charge at same time. Magnetic-force effect is one-hundredth electric force. For far-away test charges, radial electric force is smaller than disturbance force, because radial force decreases with distance squared but transverse force decreases with distance. Original-charge velocity and acceleration have only negligible effect on far test charges, because waves move at light speed but charges move much slower.
Test charges along accelerating-charge direction have no transverse effects, because push or pull is in same direction as accelerated charge.
not stationary
Stationary oscillating electromagnetic fields cannot exist, because electromagnetic induction requires field movement. Standing waves result from traveling-wave superposition.
medium
Light needs no medium, because electric/magnetic fields are their own medium.
situations: antenna
Alternating current accelerates many charges back and forth along one orientation (antenna), making transverse electric-field waves that expand in planes that go through acceleration direction. Electric-field lines transverse to oscillation direction have maximum transverse component. Electric-field line along oscillation direction has no transverse components. Electric-field lines between transverse and oscillation direction have decreasing transverse component.
Electric-field change causes magnetic-field change one quarter cycle later, by relativistic length contraction, and magnetic-field change causes electric-field change one quarter cycle later, by relativistic length contraction, so phases lag each other by 90 degrees. If magnetic-field gradient first increases to north, then electric-field gradient increases to east, then magnetic-field gradient increases to south, then electric-field gradient increases to west, and then magnetic-field gradient increases to north, and so on, because each drives the other along by transverse electric force. Inductions are at right angles, rotating around direction of motion by 90 degrees. 90-degree rotations result in linearly polarized waves.
Source charge accelerations affect electric and magnetic fields at same time, so changing electric field makes magnetic field and changing magnetic field makes electric field simultaneously, so electric field and magnetic field are always in phase.
As electric field increases, magnetic field increases, because magnetic fields are relativistic effects of electric fields. As electric field decreases, magnetic field decreases. When electric field maximizes, becomes zero, or maximizes in opposite direction, magnetic field maximizes, becomes zero, or maximizes in opposite direction. Magnetic-field and electric-field changes increase and decrease in synchrony (phase), because both fields couple. Transverse magnetic-field and electric-field accelerations are equal, in phase, and perpendicular.
When electric field and magnetic field are zero, and potential energy is zero, electric-field change and magnetic-field change maximize in space and time. When electric field and magnetic field maximize, and potential energy maximizes, electric-field change and magnetic-field change are zero in space and time. When electric-field change is zero and electric field maximizes, voltage maximizes and current is zero. When electric-field change maximizes and electric field is zero, voltage is zero and current is zero. When magnetic-field change is zero and magnetic field maximizes, voltage is zero and current maximizes. When magnetic-field change maximizes and magnetic field is zero, voltage maximizes and current is zero.
Fields elastically exchange potential and kinetic energy and make harmonic oscillations. Photons continue at same frequency.
Starting from stationary charge, voltage accelerates charge and adds kinetic energy. Increasing magnetic field increases electric field until increasing electric field has slowed increasing magnetic field and both are maximum, with potential energy maximum. The slower changing electric field decreases magnetic field, which decreases electric field, so both fall in phase, as potential energy becomes kinetic energy. As kinetic energy becomes potential energy in the opposite direction, and then potential energy becomes kinetic energy, the half-cycle repeats in the opposite direction, to complete one cycle. Oscillating current repeats the cycle, and the cycles move outward at light speed. Oscillating current induces electromagnetic waves of same frequency.
Light waves have electric-field and magnetic-field linear polarizations, at right angles. Electric field oscillates in plane that goes through charge-motion direction. Magnetic field oscillates in plane perpendicular to charge-motion direction.
Leading edge of wave rises transversely at angle determined by frequency, which depends on deceleration amount. Higher frequencies have steeper angles. Higher frequencies have greater curvatures at maximum displacement, because higher frequency means turnaround is faster.
situations: dipoles
For dipoles, charge acceleration increases as charge separation increases.
situations: atoms
Atom and molecule electrons can accelerate or decelerate and so change orbits, absorbing or making radiation. Molecule dipoles can rotate, vibrate, or translate, and so accelerate electrons, absorbing or making radiation.
situations: devices
Free charges in electric and magnetic fields accelerate free charges, as in vacuum tubes. When moving electrons hit metal plates, they decelerate and can make x-rays.
Electric-charge accelerations start electromagnetic waves {wave initiation} {initiation, wave}, because force makes radial electric field have transverse component adjacent to charge. Transverse component travels outward along electric-field line {wave propagation} {propagation, wave}, because electric-field (and magnetic-field) changes interact at light speed, because electromagnetic force is strong. Waves travel away from charges, because all energy travels outward, so no energy is left behind, and only wave leading edge (wave front) exists at any time. Wave has kinetic energy directly proportional to force that caused charge acceleration.
charge: stationary
Stationary charge makes constant electric field and no magnetic field. See Figure 1.
charge: moving
Charge moving at constant speed makes moving electric field and constant magnetic field. See Figure 2. Magnetic field is perpendicular to electric field, because magnetic field comes from relativistic length contraction that causes increased charge density along charge-motion direction, which observers see from side.
charge: acceleration
Accelerating charge increases current, because charge speed increases. Increasing current makes increasing magnetic field. Accelerating charge makes faster moving electric field. See Figure 3. (Decelerating charge decreases current, decreases magnetic field, and makes slower moving electric field.)
initiation
As charge accelerates, electric and magnetic fields accelerate, and magnetic field increases. See Figure 4.
propagation
Electric-field (and magnetic-field) change cause magnetic-field (and electric-field) gradient, by Maxwell's laws, so electric and magnetic fields interact. Interaction is at light speed. See Figure 5.
When induced electric field and magnetic field reach far-away test charge, electric-field vertical component accelerates test charge. See Figure 6.
When induced electric field and magnetic field pass far-away test charge, test charge continues at constant velocity. See Figure 7.
propagation: direction
Electromagnetic-induction is only at wave front, because all energy is there. Behind wave front, electric and magnetic fields return to zero, as fields, coming from many points with all phases, cancel. Waves propagate outward from accelerated charge, because electromagnetic-induction electric and magnetic fields behind have all phases and cancel.
propagation: no medium
Electromagnetic waves can propagate through empty space, because electric and magnetic fields are their own medium.
propagation: induction rate and wave speed
Electric-force strength determines electromagnetic-induction rate, which is light speed. Material electric charges, relativistic apparent electric charges, other electric fields, and other magnetic fields exert force on electromagnetic waves, and so reduce electromagnetic-wave speed.
Unaccelerated Charge Makes No Electromagnetic Wave
Unaccelerated moving charge makes moving constant electric field and constant concentric magnetic field. See Figure 4. No acceleration makes no force, so fields stay constant. Only radial force affects test charge, so it has no transverse motion.
Charge Acceleration Makes Traveling Electric Field
See Figure 5. Collision, gravity, or electric force can accelerate charge. Acceleration makes force, so fields change. Acceleration is transverse to radial electric-field line, so test charge has transverse motion. See Figure 6.
pure electric waves
There are no pure electric non-magnetic waves, because waves require electric-field changes, which always make transverse relativistic electric fields, which are magnetic fields. There are no pure magnetic non-electric waves, because waves require magnetic-field changes, which always make transverse relativistic electric fields.
Waves {light}| {electromagnetic wave} can begin by charge accelerations or electronic transitions and propagate by electromagnetic induction. Charge-acceleration or electronic-transition energy change determines electromagnetic-wave frequency.
Accelerating charge makes a photon field, which differs near source {near field} and far from source {far field}. Far field is what lenses, mirrors, and instruments see. Point charges or nearby detectors can examine near field.
Equations {Maxwell's equations} {Maxwell equations} can find all electric and magnetic properties. For stationary and moving charges, electric-field and magnetic-field relations are Gauss's law, Gauss's law for magnets, Faraday's law, and Ampere's law.
stationary
Partial derivative of electric field with distance equals negative of partial derivative of magnetic field with time. Partial second derivative of electric field with distance equals electric permittivity times magnetic permeability times partial second derivative of electric field with time.
tensors
Maxwell's equations are equivalent to two equations. For magnetostatics and magnetodynamics equations, exterior derivative of electromagnetic-field tensor F equals zero: dF = 0. Electromagnetic-field tensor is a linear operator on velocity vector. Electromagnetic-field tensor has covariant components. This tensor is equivalent to delta function. For electrostatics and electrodynamics equations, exterior derivative of electromagnetic-field-tensor dual F* equals four times pi times four-current dual J*: dF* = 4 * pi * J*. This tensor is equivalent to delta scalar product.
current
The four-current has one component for charge density and three components for current densities in three spatial directions.
duals
Rank-x antisymmetric tensors relate to rank 4 - x antisymmetric tensors {dual, tensor}. Dual of dual gives original tensor, if rank is greater than two.
invariant
Electromagnetism invariant is current squared minus light speed times charge density squared, which equals negative of momentum times light speed squared.
retarded and advanced
Electromagnetic-field changes follow charge accelerations {retarded solution}. However, field changes can happen before charge accelerations {advanced solution}, because equations are symmetric. Other solutions can be linear retarded-solution and advanced-solution combinations.
Light speed {speed of light} {light speed}| is the same relative to any observer, moving or not. Light speed is invariant and absolute, in space with no electric fields.
speed
Light speed depends on electric-force strength, which determines electromagnetic-induction strength. In vacuum, light speed is 3.02 x 10^8 m/s (Hippolyte Fizeau and Bernard Foucault) [1849]. Light speed is fast, because electric forces are strong. All zero-rest-mass particles travel at light speed, because added energy does not affect them. Gravity does not affect zero-rest-mass particles.
space
Light does not travel through time, because it has no medium and so no reference frame or space-time. Light only travels through space, not time. Light has zero time.
cause
Observers see invariant speed, because light never has time component and so cannot go slower. Light cannot go faster, because it uses all of space already. When observers see light, light length appears to be zero and time appears to be at maximum dilation. Observer motion does not affect light speed observed, because light has no medium. Observer motion contracts length and dilates time, but light already has maximum length and shortest time. If observer moves at higher velocity, both time dilation and space contraction happen, so light speed stays the same.
space-time velocity
All objects travel through space-time at light speed. Light travels only in space. Stationary objects travel only in time. Moving masses travel in space and time.
terminal velocity
Light speed is like terminal velocity through space-time. Electromagnetic induction pushes wave, and forces in universe retard wave. Resistance to light motion can come from effects of all universe masses and charges.
mass
No object with mass can go faster than light. For mass at light speed, stationary observers see infinite mass, zero length, and zero time. To make infinite mass requires infinite energy. Infinite mass exerts infinite gravitational force. Infinite mass attracts and red-shifts light, dimming universe. Infinite mass, moving at light speed, appears to have infinite frequency and zero wavelength.
phase velocity
Light pulses contain wave sets. Light-pulse envelope carries energy. Envelope speed {group velocity} must be light speed or less. However, individual waves can have speed higher or lower than light speed {phase velocity}. Negative refraction cannot exist.
Perhaps, light travels in a stationary medium {luminiferous ether} {the ether} {æther}, not vacuum. As such, because light has constant velocity in any reference frame, ether is an absolute reference frame. It is fluid but does not disperse, has no viscosity, and has high tension and is rigid. It has zero rest mass and is transparent, continuous, and incompressible. Perhaps, it appears rigid to high-velocity objects or high-frequency waves but fluid to low velocity objects or low-frequency waves. Michelson and Morley [1887] measured interference of light traveling in Earth-motion direction and in opposite direction {Michelson-Morley experiment} and found no interference and no Doppler effect, leaving no physical properties to ether and so indicating that there was no ether.
Light can carry enough electric energy to knock electrons out of atoms {photoelectric effect}|. If light frequency is below threshold for material, atoms emit no electrons, because photoelectric effect requires minimum energy. Light with higher frequency than threshold imparts more speed to liberated electrons but does not emit more electrons. Higher-intensity light, which has more photons with enough energy, makes more electrons leave.
Radiation has entropy {entropy, radiation} {radiation entropy}. If space is isotropic and unpolarized, entropy S equals four times energy U divided by three times temperature T: (4*U) / (3*T). If system has more wavelengths or more directions, radiation entropy increases. Universe can absorb radiation and everything else without limit, so entropy continually rises.
Light has subatomic particles {photon, light}|. Photon is like wave packet. Continuous light {light ray} {ray, light} is many wave packets.
straight
Light rays and photons travel in straight lines.
energy
Photon energy E is frequency v times Planck constant h: E = h*v.
observers
What do people see as photon goes past? In empty space, people see particle contracted to zero length, with no mass but with frequency and wavelength. People see time standing still on photon.
What does photon see? In empty space, photon travels at light speed. Other objects pass by at light speed, with infinite mass and zero wavelength. Photon sees time as standing still on other things. Photon sees only point straight-ahead, and sees nothingness on sides, so photon sees along one-dimensional line.
Light can travel in two dimensions {plasmon}| and so travel in plane. Photons that hit interface between conductor and insulator induce surface electrons to vibrate at same or similar frequency and cause traveling wave. Wave reflections make resonances. Plasmons {plasmonics} can have same or shorter wavelength as impinging light.
Light intensity {illuminance}| is light flux (in lumens) per area. Light intensity depends on amplitude squared, photon number, and frequency squared.
Light intensity {Poynting vector} has maximum of half times light speed times permittivity e times electric field E squared: 0.5 * c * e * E^2. Poynting vector equals half times electric field E times magnetic field H: 0.5 * E * H.
At high intensity, wave electric field can affect molecule electric fields {Kerr effect} {optical Kerr effect}.
Radiation has pressure {radiation pressure} {pressure, radiation} from photon flow. Pressure P equals energy U divided by three times volume V: P = U / (3*V).
Light meters {photometer}| can measure light intensity.
Radiation has frequency {radiation frequency}.
Deceleration as electrons hit metal makes radiation {Bremsstrahlung radiation}| with wavelength 10^-12 meters.
Beta-particle electrons, with velocity higher than light speed in water, emit blue light {Cerenkov radiation}| {blue glow} as shock waves when they enter water. Water surrounding nuclear-reactor cores, which emit high-velocity electrons, has blue glow.
process
Electrons traveling in water use some energy to polarize water molecules along travel direction. After electrons pass, polarized water molecules emit light. If electrons travel slower than light speed in water, emitted radiation appears low, because electromagnetic waves emitted by molecules along path are random and destructively interfere. If electrons travel faster than light speed in water, emitted radiation appears high because electromagnetic waves emitted by molecules along path are shock waves that constructively interfere.
Infrared-light rotational and vibrational energies cause differences in visible light reflected from molecules {Raman scattering}|.
In atmosphere, secondary cosmic rays {spallation}| arise if cosmic ray hits atomic nucleus.
Charged particles accelerated by spiraling in magnetic field can emit microwaves {synchrotron radiation}|. Synchrotron radiation happens when electric field is parallel to electron-orbit plane.
Electromagnetic radiation has frequency range and wavelength range {spectrum, light}|.
low frequency
electric wave. radio wave. short wave. very-high-frequency TV wave. ultra-high-frequency TV wave. microwave radiation. infrared ray.
visible
Visible light is 4 x 10^14 Hz with wavelength 6.8 x 10^-7 meters for red light, orange, yellow, wavelength 5.5 x 10^-7 meters for yellow-green, green, wavelength 4.4 x 10^-7 meters for blue light, indigo or ultramarine, and 7.5 x 10^14 Hz with wavelength 4.1 x 10^-7 meters for violet light.
Violet is 380 to 435 nanometer, with middle at 408 nanometer. Blue is 435 to 500 nanometer, with middle at 463 nanometer. Cyan is 500 to -520 nanometer, with middle at 510 nanometer. Green is 520 to 565 nanometer, with middle at 543 nanometer. Yellow is 565 to 590 nanometer, with middle at 583 nanometer. Orange is 590 to 625 nanometer, with middle at 608 nanometer. Red is 625 to 740 nanometer, with middle at 683 nanometer.
high frequency
near ultraviolet. ultraviolet. far ultraviolet. X ray. gamma ray. secondary cosmic ray. cosmic ray. primary cosmic ray.
Smallest frequencies and longest wavelengths {electric wave}| are 3 to 60 Hz and 10^8 to 5 x 10^6 meters.
Next smallest frequency and wavelength {radio wave}| are 10^3 Hz and 3 x 10^5 meters.
High-frequency radio waves {short wave}| are for global communication.
Typical TV frequencies and wavelengths {very high frequency TV wave}| (VHF) are 10^8 Hz and 3 meters.
higher TV frequencies and wavelengths {ultra high frequency TV wave}| (UHF).
frequencies below infrared {microwave radiation}|.
Heat-ray {infrared}| frequency is 10^12 Hz, with wavelength 3 x 10^-4 meters.
Light {visible light}| can have wavelength 400 nm to 700 nm. Visible light has same wavelengths as diameters of, and energy changes in, atoms and molecules. Matching diameters allows people to focus on objects, because light is not too diffracting or too strong. Matching energy changes allows absorption, emission, and chemical reactions.
Smallest visible-light frequency {red light}| is 4 x 10^14 Hz, with wavelength 6.8 x 10^-7 meters.
Highest visible-light frequency {violet light}| is 7.5 x 10^14 Hz, with wavelength 4.1 x 10^-7 meters.
higher frequency than violet {ultraviolet}|.
Light {far ultraviolet}| {black light} can have frequency 1.5 x 10^15 Hz and wavelength 2 x 10^-7 meters.
higher frequency than far ultraviolet {X ray}| {x ray}.
Next-to-highest frequency {gamma ray, spectrum}| is 10^23 Hz, with wavelength 3 x 10^-15 meters.
Highest frequency {cosmic ray}| {primary cosmic ray} is 10^25 Hz, with wavelength 3 x 10^-17 meters. Quasars and powerful energy sources make cosmic radiation.
Light {monochromatic light}| can have one wavelength.
Light {polychromatic light}| can have many wavelengths.
Magenta, yellow, and green pigments {primary pigment}| mix to make black.
Variations {dichroism}| in absorbed-light color can depend on light-polarization direction. Dichroism indicates molecule orientation, which can be linear, circular {circular dichroism}, or elliptical. Microvilli rhabdom can lie parallel, exhibit dichroism, and detect polarized-light polarization plane.
If one photon accelerates, light-wave electric field vibrates in one plane {plane polarized wave} {polarized light}, and light-wave magnetic field vibrates in perpendicular plane {polarization, wave}|. Typically, many charges accelerate in all possible planes, so there is no polarization.
materials
Materials can allow only light with one electric-field plane to transmit. Polaroid plastic and tourmaline can polarize light.
circular
Asymmetric-molecule electric forces cause substances to rotate electric-field planes {circularly polarized wave} around light travel direction.
Optical activity can vary with light frequency {dispersion, light}|. Higher frequencies cause more rotation, because photons have more energy.
If polarized light with different wavelengths passes through asymmetric medium, shorter wavelengths rotate plane more than longer wavelengths {optical rotatory dispersion} {Cotton effect}.
Materials with asymmetric-molecule electric forces can have refractive index different for left and right circularly polarized light {optical activity}|. Carbon can bond four different atoms, in two mirror-image forms.
Light takes shortest path, and so least time, between two points {Fermat's principle} {Fermat principle}.
Action is energy times time, or momentum times distance, or angular momentum times angle. Light uses path with least action between two points {Hamilton's principle} {principle of least action, Hamilton} {least-action principle, light}|. In quantum mechanics, action has quanta, which have size Planck constant h, so photons have energy quanta h * frequency, momentum quanta h / wavelength, and angular-momentum quanta h / 2 * pi.
Lasers produce light waves {coherent light}| that have same phase.
Light passed through consecutive slits {collimate}| has many light waves in phase.
Devices {laser}| {Light Amplification by Stimulated Emission of Radiation} can emit many photons in phase [1960].
light source
Flash tube excites atom electrons into highest orbital. Below highest orbital are one or two lower-energy levels, and below them is ground-state level.
light
Electrons spontaneously fall to intermediate-energy level by vibration, rotation, or radiation.
Then previous photon causes electron to fall to next-lower level {lase}, which simultaneously makes another photon, so both photons are in phase and photon number doubles. This process repeats to make many in-phase photons. Lasers can emit light axially or transversely.
collimation
Photons conserve momentum, so they have same direction.
amplitude
Mirrors can build power by repeated lasing and reflecting, until shutter opens {Q switching} and light releases. Shutter can be rotating mirror, Pockels cell, photochemical, or exploding film. Current modulation can modify laser amplitude. Lasers can pulse or be continuous. Laser can be tunable to different light frequencies.
materials
Lasers can use helium-neon, helium-cadmium, argon, krypton, carbon dioxide, and gallium arsenide. Ruby lasers emit red light. Gallium-nitride lasers emit blue light. Zinc selenide can also make blue light.
purposes
Lasers can align exactly, measure distances by reflection from corner reflectors, attach retinas by burning them on, weld, and make holographs. Lasers can separate atom isotopes, by exciting only one isotope. Lasers can measure thickness, drill holes, and carve miniature circuit blocks. Lasers can implode pellet to start nuclear fusion in tube {hohlraum}.
fiber optics
Laser light passed down non-linear optical fiber {microstructure fiber} broadens in wavelength {supercontinuum light}. Light can alter material, which then alters light {self-phase modulation}.
timing
Lasers {mode-locked laser} can make one-femtosecond microwave or light pulses at 1-GHz. Frequencies are visible light within 150-nm wavelength interval. Superposition makes pulses have few wavelengths. Phase {offset frequency} increases slightly with each pulse. Wave-train pulses have higher net frequencies until cycling again, with equal spacing. Pulses are beats, so pulse frequency is lower-frequency frequency difference. Given reference frequency, beat frequency can determine unknown frequency.
Storing light-wave interference patterns {hologram}| on photographic plates {holograph} allows display of three-dimensional images [Gabor, 1946].
production
Coherent light can shine directly on photographic plate and can reflect from static scene onto plate. Wave-front superposition makes interference pattern that photographic plate can record.
projection
Shining coherent light on or through photographic plate can project scene wave front into space. Plate positions contribute to all image points, whereas photograph points contribute to one image point. Observer sees wave front coming from three-dimensional space, rather than from surface. Observer can view image from different points to see image from different perspectives.
Shining coherent light on part of plate makes whole image but with lower resolution, because number of contributions is less, so standard error is more. Using longer-wavelength coherent light to reconstruct image can magnify image size. Using shorter wavelength coherent-light to reconstruct image reduces image size.
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Date Modified: 2022.0225