Naked Science Forum
Non Life Sciences => Technology => Topic started by: Paul Gamble on 07/06/2018 18:55:47
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Lasers are cool. 8) One thing I wonder though is, photons do not have mass but they do have energy. Energy is equivalent to mass, so when a laser beam is pumped and then discharged is it releasing more photons or higher charged photons with more energy?
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Mass is not the important thing. It is the inertia of the photon. The momentum does not depend upon an inertial mass. You could say that the inertia of a photon is the universal minimum that an object can possess. The magnetic and electric constants are the limiting constraints on photon velocity. So these properties together guarantee a constant speed for light in free space.
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higher charged photons
Photons are not charged.
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Mass is not the important thing. It is the inertia of the photon. The momentum does not depend upon an inertial mass. You could say that the inertia of a photon is the universal minimum that an object can possess. The magnetic and electric constants are the limiting constraints on photon velocity. So these properties together guarantee a constant speed for light in free space.
That makes sense. but really what I am wanting to know is what happens when you "Pump" a laser and then fire a pulse. Is the diode sending out electrons and photons? How does the energy from the capacitor bank add power to the laser? "Say" I had a 1 watt diode hooked up to a flash lamp circuit that was working as a relay between the laser and my energy bank and I had a car ignition to discharge the energy bank into my laser. When it pulses is it releasing more photons/electrons, or is it because the amount of energy discharged is applied over a shorter period of time. More energy would mean more inertia but is the laser still making the same amount of particles? That is really what I want to know.
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what I am wanting to know is what happens when you "Pump" a laser and then fire a pulse. Is the diode sending out electrons and photons?
The laser is sending out photons. The energy of an individual photon defines its frequency which we see as a specific colour. The intensity of the beam, its brightness and total power is due to the very, very large number of photons emitted, the more the brighter, the greater the power of the beam. That’s it in a nutshell.
Hope that helps
PS the correct term Jeff used in his reply is momentum not inertia.
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what I am wanting to know is what happens when you "Pump" a laser and then fire a pulse
Most atoms on Earth spend most of their time in the "ground state", ie the electrons are in the lowest energy level, and can't go any lower.
You can bump an electron into a higher energy level (eg by hitting the atom with a photon or an electron), but it will pretty quickly drop down to a lower level, emitting a photon (sometimes several photons, of lesser energy).
"Pumping" a laser means getting many electrons into a higher energy level, which is carefully chosen so it takes longer-than-usual for them to drop back down. This is called a "population inversion". Then just one electron dropping back down will emit a photon that triggers many other electrons to drop back down, emitting a pulse of laser light with a common frequency and phase.
There are many techniques to pump a laser, including a bright flash of light, an electrical current or even a chemical reaction.
See: https://en.wikipedia.org/wiki/Laser_pumping