Talk:Franck–Hertz experiment

killed dead link
The "up-to-date-literature" link was dead (the one to http://users.skynet.be/P.Nicoletopoulos/references.html). In fact, there is no skynet.be at all anymore, though it remains registered.

I've removed the link. Epistemenical (talk) 01:16, 4 April 2008 (UTC)

Incorrect physics
Surely the explanation for the 2nd peak at 9.8V is wrong? "2 simultaneous inelastic collisions"? We are told that this peak-trough behaviour continues to 100V or more; what is the explanation at 98V? 20 simultaneous inelastic collisions??

No. At the point in the tube where the potential is 4.9, the electrons (or most of them) give up all their energy to exciting mercury atoms. They then accelerate from the 4.9V point, starting again from near-zero energy. At the 9.8V point they have each once again acquired 4.9eV. At this point they (or most of them) give up all their energy once more. This proceeds to higher and higher voltages, with most electrons never gaining more than 4.9eV.

I did my physics yonks ago. Can any smart academic check this, please! 27 Aug 2008

"A similar pattern is observed with neon gas, but at intervals of approximately 19 volts."

This is blatantly wrong. Intervals of 19 volts would mean that neon produces emission spectrum of 65 nanometers. That is within the range of extreme ultraviolet rays. If this were true, people conducting this experiment with neon would have become HULKS by now.

Electrons drop from 19.5-19.3 eV to 16.57 eV which means about 2 Volts of interval. Do some math and here is the reference

http://hyperphysics.phy-astr.gsu.edu/hbase/frhz.html — Preceding unsigned comment added by 50.131.88.248 (talk) 09:29, 14 May 2012 (UTC)

_____________________________________________________________________________________________________________________ in the current vs voltage graph;why at the Ionisation Potential points the slope does not fall sharply,about horizontally to the x-axis?210.212.6.2 (talk) 06:28, 9 September 2008 (UTC)

210.212.6.2 (talk) 06:26, 9 September 2008 (UTC)

Current and electron speed
The article states: "Larger voltages yield larger electron speeds, and larger currents are measured because the time required for an electron to travel from the cathode to the anode is reduced."

This is a flawed argument. The measured (equilibrium) current cannot(!) depend on the speed of the electrons between the electrodes. It depends on the rate of electrons arriving at the anode, which must be given by a fraction of the rate of electrons leaving the cathode. If this fraction were 100%, the current would be determined entirely by the rate of electrons leaving the cathode and could not depend on any subsequent dynamics. The current can only rise, if this fraction changes. This means that the current depends on the statistical properties of the thermal electron gas. Some electrons must find their way back to the cathode via other paths than via the anode (via the grid, or directly back to the cathode). The correct argument must be that depending on velocity-dependent inelastic collision rates the velocity distribution is changed, which in turn changes the fraction of electrons being able to pass the grid. In addition, there may be space charges accumulating that will repel an increasing fraction of electrons, which then will not reach the anode. The statistical properties (distribution of speeds) is also the reason for the smooth transitions instead of sharp kinks in the current vs voltage graph.

Maybe a more obvious example for this argument is this: If 100 people leave Los Angeles every day to move to New York, then the influx of people to New York is 100 people per day, no matter if they walk, drive, take a train, or fly.

7. April 2018 146.198.14.85 (talk) 21:04, 7 April 2018 (UTC)


 * Yep, that statement was indeed nonsense. I've removed it. TenOfAllTrades(talk) 03:38, 8 April 2018 (UTC)