Does light actually travel through space?
Yes. Light really travels through space. Light propagates as spherical waves of energy carrying energy radially outwards from its source. There are trillions of waves in just one second passing through space, each kicking the one in the front. The distance between two waves ( we call it wave length) is extremely small. Its frequency ranges in trillions per second. This is how light makes it own medium to propagate. This is why light does not need any other medium. There is no other medium so compact. While traveling through space, light encounters various energy fields, objects with mass which absorb its energy. After traveling through space for a long time, light gets red shifted. We do get highly red shifted light from galaxies 13.8 billion light years away. This light did pass through space. Light travels at 300,000 km per second. It has speed. This also indicates that light always travel through space. It does take time to travel from one point to other point in space. Space exists. It is continuous through out the universe. It cut through all objects in space. It is inside and out side of atoms, planets, stars, galaxies, etc. Nothing exits without space. Light needs space to travel through.
Why does accelerating charge radiate electromagnetic radiation?
The fact that accelerating charged particles emit electromagnetic radiation demonstrates one of the deepest aspects of electromagnetism.Charged particles are “sources” for the electromagnetic field. This means, they create an electromagnetic field that is tied to them and that electromagnetic field propagates out. If a particle is sitting still (which is equivalent thanks to Special Relativity to a particle moving at a constant speed), the field will be a Coulomb field falling off like 1/r and be time-invariant. An accelerating charge causes the electromagnetic field to develop “kinks” and these kinks aren’t stationary and propagate out as electromagnetic radiation.Basically, charged particles have streamers attached to them and if you give them a yank, the streamers will come off. Those separated streamers are the radiation. The energy in the radiation comes out of the force that is accelerating the particle.This is picture is captured in the Liénard–Wiechert potential, which is a fully relativistic formulation of the electromagnetic fields are that are created by an arbitrarily moving particle. [1] The Liénard–Wiechert potential is frequently not covered in undergraduate electromagnetism courses and typically has to wait until graduate electromagnetism courses.A good book that gets to this physics quickly without getting bogged down is Barut’s Electrodynamics and Classical Theory of Fields and Particles [2] which is happily available for less than $6.50.Footnotes[1] Liénard–Wiechert potential - Wikipedia[2] Electrodynamics and Classical Theory of Fields and Particles (Dover Books on Physics): A. O. Barut, Physics: 9780486640389: Amazon.com: Books
When photons travel through glass, their speed is reduced. When they exit the glass, e.g. into a vacuum, their speed will be higher. What gives them the energy to accelerate?
Photons travel at the speed of light (c) in a vacuum. When light enters a medium such as glass, the light beam (composed of photons) slows down in forward speed (v), the wavelength (λ) is shorter but the frequency (υ) remains the same. Since the frequency stays contant in the medium the light does not lose energy according to E=hυ. The forward speed of the light beam is reduced depending on the index of refraction (n) of the medium. For flint glass, n=1.62, where n in a vacuum is unity, the velocity of light in glass is n=c/v, or v = c/n. Here the index of refraction is defined as the speed of light in a vaccum divided by the speed of light in a medium. This equation can be expanded using (c=λυ), λυ/λ’υ’ = c/v, (here υ=υ’), so λ/λ’=c/v, or λ/λ’ = n, λ’=n/λ. The wavelength of the light beam in the medium is shorter by n/λ. When light emerges from the medium back into a vaccum, the state of the light is the same as before it entered except for a decrease in intensity according to Beer’s Law, I = Io[exp]-cz, where Io = original intensity, c = total attenuation coefficient, where c = a+b, a = absorption, b = scattering, z = thickness of the medium, 1/c= one attenuation length. In water, n=1.33, it becomes difficult to see another diver after four attenuation lengths. In very clear water where c=0.1, four attenuation lengths is 4/0.1 = 40 meters, see Jerlov.
Can a charged particle moving with a constant velocity produce both electric and magnetic fields?
A charged particle produces an electric field. This electric field exerts a force on other charged particles. Positive charges accelerate in the direction of the field and negative charges accelerate in a direction opposite to the direction of the field.A moving charged particle produces a magnetic field. This magnetic field exerts a force on other moving charges. The force on these charges is always perpendicular to the direction of their velocity and therefore only changes the direction of the velocity, not the speed.An accelerating charged particleproduces an electromagnetic (EM) wave. Electromagnetic waves are electric and magnetic fields traveling through empty space with the speed of light c. A charged particle oscillating about an equilibrium position is an accelerating charged particle. If its frequency of oscillation is f, then it produces an electromagnetic wave with frequency f. The wavelength λ of this wave is given by λ = c/f. Electromagnetic waves transport energy through space. This energy can be delivered to charged particles a large distance away from the source.
Resonant frequencies?
After a little bit more studying to come to a better understanding of how the greenhouse effect works and how a increase in greenhouse gas concentration leads to a greater warming of the atmosphere I came across this term: resonant frequencies. My understanding is that within quantum mechanics each electron surrounding each individual atom can only orbit around the atom at predefined orbits. When an electron absorbs a photon of energy it jumps to a higher orbit. When it loses a photon of energy it jumps to a lower orbit. When the photon is lost the path of departure is random. However it generally goes in about the same path it was absorbed from with some exceptions. I also learned that each orbit is determined by the smallest orbit. Each orbit on top of the is just a multiple of that original orbit. Exactly how is that original orbit determined? What exactly forces the electron to orbit at that particular distance? What determines what frequency the re-emission of the photon of energy is emitted at? How is this related to the greenhouse effect?