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Physics, Astronomy & Cosmology / Re: Why isn't visible light considered ionizing radiation?
« on: 19/09/2017 20:20:37 »
Visible light has insufficient energy (under normal circumstances). At 400nm (Deep violet high energy light) the light has, if my calculations are correct around 5E-7J/photon or 300KJ/mole. Since the ionization energy of sodium is just under 500KJ/mole, the light is therefore of insufficient energy.
However, by applying a voltage (negative) to the sodium of just a few volts, we can make up the energy difference. The 20V of a DC power source can deliver, If my logic/math is correct, just over 1900KJ/mole, which means at that value, only a few of those 20Volts would be needed to cover the difference.
Thinking of it in non-quantized perspective, by forcing a bunch of electrons into the same place on the sodium, the repulsion helps assist in launching them off the metal, so a low energy visible light can be used.
However, by applying a voltage (negative) to the sodium of just a few volts, we can make up the energy difference. The 20V of a DC power source can deliver, If my logic/math is correct, just over 1900KJ/mole, which means at that value, only a few of those 20Volts would be needed to cover the difference.
Thinking of it in non-quantized perspective, by forcing a bunch of electrons into the same place on the sodium, the repulsion helps assist in launching them off the metal, so a low energy visible light can be used.