Why cant a free electron absorb a photon?
A free electron cannot absorb a photon as it is not possible to satisfy the energy and momentum conservation simultaneously. In Compton effect we have both electron and a photon as the final product and it is then possible to conserved energy and momentum.
Why can’t a single photon produces an electron positron pair?
So to create a new mass, all you need is energy. Let us take the same example you have quoted in the question. You cannot create an electron and a positron (or any pair of particles) using a single photon because the kinematics of special relativity just doesn’t allow it.
How do free electrons interact with photons?
Photons interact with electrons to increase the energy of the electron. As the electron returns to a stable level, it emits a photon, which is why we see things like colour.
Why can’t electron positron pair production process occur in vacuum?
Originally Answered: why does pair production cannot occur in vacuum? Because the pair production is a concept of conservation of energy and momentum. But in vacuum we can’t conserv it . In vaccum we don’t want any any type of KE energy to move in the absent of the air.
Why pair production does not take place in vacuum?
@Lin Zhang, in the case of pair production in vacuum, it is impossible to satisfy both momentum and energy conservation, or if momentum is conserved, not so is energy.
How does a single photon move?
Photons are massless, so they always move at the speed of light in vacuum, 299792458 m/s (or about 186,282 mi/s). Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, their behavior featuring properties of both waves and particles.
Can a single photon interfere with itself?
A single photon can only interfere with “itself”. However, “itself” is ill-defined because all photons are identical in quantum mechanics. Because of their Bose-Einstein statistics, the wave function of all photons is symmetric – invariant under all permutations of the individual photons.
What are the reasons why electrons are released or emitted?
In the photoelectric effect, electrons are emitted from matter (typically metals and non-metallic solids) as a consequence of their absorption of energy from electromagnetic radiation of high frequency (short wavelength), such as ultraviolet light.
Can an electron give off energy in a vacuum?
But an electron can only do electromagnetism (ignoring its gravitational and weak interactions, since those are waaaaay to weak to matter). If we now make the electron’s momentum change by exposing it to an electric field in the vacuum, it can only give off its energy and momentum to a real photon – which is light.
Why don’t electrons absorb photons?
They are tightly controlled by an oscillating magnetic field, so that they emit coherent radiation. An electron can’t absorb a photon all by itself, because you can’t get conservation of energy and momentum with the electron alone.
Can a free electron absorb light?
it is true that a free electron cant emit or absorb a photon but it is misleading to think that a free electron is totally unaffected by the passage of a light wave. the electron will indeed oscillate but it will always emit exactly the amount of energy that it absorbs. the ‘net’ effect is that it is unaffected.
Why does an electron not emit a photon at constant velocity?
At the given established velocity in your chamber, that electron does not experience any extra vibrations (ie it is in equilibrium) and has no reason to emit a photon.