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Thread: Quick question regarding the PHOTOELECTRIC EFFECT

  1. #1 Quick question regarding the PHOTOELECTRIC EFFECT 
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    I'm reading many different things on this topic and it seems pretty easy to understand, as far as a photon having the frequency to "knock off" an electron. The thing is, I also read things regarding quantum leaps and I want to know where they meet. So when an electron is "knocked off" by a photon is it really just going to a higher orbit? Or does it leave completely, and if so where does it go?

    This kind of leads to another question. What defines an atom? Obviously the protons and neutrons, but I assumed the number of electrons had something to do with its makeup. So do atoms actually gain and lose electrons constantly based on the light hitting them?

    any help would be greatly appreciated.

    Jim


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  3. #2 Re: Quick question regarding the PHOTOELECTRIC EFFECT 
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    Quote Originally Posted by jim35meyers
    I'm reading many different things on this topic and it seems pretty easy to understand, as far as a photon having the frequency to "knock off" and electron. My The thing is, I also read things regarding quantum leaps and I want to know where they meet. So when an electron is "knocked off" by a photon is it really just going to a higher orbit? Or does it leave completely, and if so where does it go?

    This kind of leads to another question. What defines an atom? Obviously the protons and neutrons, but I assumed the number of electrons had something to do with its makeup. So do atoms actually gain and lose electrons constantly based on the light hitting them?

    any help would be greatly appreciated.

    Jim
    If there is sufficient energy given to an electron then it can overcome the forces (electromagnetic) that want to confine it to an orbital in an atom an it can become free. That leaves behind a positively charged ion that will in all likelihood capture a free electron from somewhere else. The free electron goes on its merry way until it is captured by another atom or ion. Free electrons are what make vacuum tubes work. There they are liberated by thermal energy -- that is what the heater in the tuve does and why they glow.

    If the photon imparts only a little more energy then the eletronis raised to a higher energy state within the same atom. That is what happens when a laser is "pumped" before it is discharge by stimulated emission.

    An atom is generally considered to be a nucleus plus a number of electrons that are bound to it resulting an overall neutral charge. If the number of electrons is not sufficient to neutralize the charge it is called a positive ion. If there are too many electrons is called a negative ion.


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  4. #3  
    Geo
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    "Knock off" means excited. Electrons, in many electron atoms exist in different energy levels, a photon provides energy to an electron, which causes an electron in the ground state to become excited. It will go into a higher energy level which is the excited state, when it returns to its ground state a photon of lower frequency is released.

    Atoms become ionised when the electrons "leave completely". Ionising radiation - high frequency EM waves - can cause atoms to lose electrons.
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    thank you so much. If there are not enough electrons to neutralize the atom, is that where something like static electricity comes from. I apologize if this is elementary, but I've just started reading about it.
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    An interesting thing can happen to ions within a charged Faraday cage. Such a structure merits attention as the default hosting venue in most cases. Hence, a charged particle is unlikely to wander aimlessly. If such a body had a negative charge, it would apply a global repulsive force that would push a dislocated electron toward the outer surface of the cage. Were the electron far enough from the positive ion it left behind, that global push would exceed the force of attraction between the ion and the loose electron to thereby move the electron toward that outer surface. In such a case, the positive ion involved would migrate into the opposite direction: toward the electrical center of the cage. Such phenomena can provide stable rearrangement of charged particles into concentric grouped configurations of significant scale.

    It doesn't seem that this information has come to the attention of any celebrity scientists so far, but the facts of true science can be self-explanatory.
    "Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense." --Buddha (563BC-483BC)
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    Please note that ionisation can be caused by any photon that at least has the minimum energy that is needed to remove an electron. However, excitation (lifting an electron to a higher orbital) can only be done by a photon that has exactly the energy that is needed to achieve that. This is the reason why absorption spectra tell you, what the absorbing material is, because only those photons are removed from the radiation that match the energy difference between electron orbitals within the atoms that are irradiated.
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