-------- By increasing the voltage in the Franck-Hertz experiment we reach a breakdown voltage in which the current existent between the grid and anode is canceled. This breakdown voltage will be repeated at equal intervals by increasing the voltage.
I. Introduction
--------------- As an evidence that even absorption of kinetic energy by an atom is quantized the Franck-Hertz experiment is cited. It is said that this experiment shows clearly that the kinetic energy of an electron colliding with an atom will be absorbed by the atom only when it is exactly equal to the distance between the energy levels of the electron in the atom. In other words, only when it has some definite amounts it'll be absorbed by the atom. What this article is going to show is that what occurs in this experiment is not really a quantum process but a simple mechanical and electric one rather similar to when you are trying to separate the apples of an apple tree by shaking its trunk. When your energy exerted on the trunk is not sufficient (equal to a definite amount) no apple will fall, but when it is the case, suddenly many apples will fall.
II. Analysis of the Franck-Hertz experiment
------------------------------------------- In the Franck-Hertz experiment, as shown in Fig. 1, the grid G is located near the Anode A while the high potential difference V between G and the cathode C is variable but the low potential difference between A and G is constant.
|-----------------------------------------| | C G | ^^^^^^^^\\ | : A | | | | : | | | | | : |-------| | | | : | | | _______/ | : | / \\ |-----|------------------------------|----| ( I ) | /^\\ | \\ / |---------( V )----------------| V' | | \\_/ | | | | |---------------| ... |--------|--||-----| | a | - + +- Fig. 1.
The gas under experiment is in the lamp containing C, G and A. When C is warmed up (electrically), the experiment starts. Variation of I, the current of A, with V is something like what is shown in Fig. 2 in which the horizontal distance between each two adjacent tops is the same.
/^\\ | | | I | .'` .'` .'` .'` | . | . | . | . | | _-` ' _-` ' _-` ' _-` ' | .- ` .- ` .- ` .- ` |/` ,/` ,/` ,/` ---|---------------------------------------------------------->
| V
Fig. 2.
The curve falls abruptly after each top (not quite normally but with a steep gradient).
As I have explained in Articles 9 and 12 and 1st appendix of the book, electric current is a continuous process, in which an electron train is moving (ie as if the electrons, taking part in the current, are in touch with each other in a train of themselves each exerting force on the next), not a colliding one. Let's remove the grid G temporarily. In this state, when the cathode C has not yet been warmed no current flows in the circuit. But when as a stimulation C is warmed, a current of electrons will flow in the circuit in the direction from C to A. Why? Because, the constant voltage V' is smaller than V and then the situation is as if the source of potential in the circuit is a single battery which its negative pole is connected to C and its positive pole is connected to A. Thus, certainly we shall have an electron current from C to A when the cathode is warmed. In this state let's restore G. Certainly, now, only a part of the current will flow via the grid toward the point a, and the rest of it still flows toward A (through the holes in the grid).
Now let's consider the right circuit consisting of G, A and V' before warming the cathode up, ie before causing any current to flow in the circuit. In this state, what can cause an electron current to flow in this (sub)circuit from A to G? Just the same factor that causes an electron current in the main circuit from C to A, ie (the stimulation caused by) heat. But we have not given any external (electric) heat to the space between A and G as done in the main circuit when warming C up. That's right, but such a heat can be provided by the electric current flowed in the space between G and A. Such a heat should be sufficient if it is to cause freedom of the electrons of the atoms of the gas from these atoms and an electron current in the right (sub)circuit from A to G, otherwise there won't be such a current even though the space between G and A is warmed (insufficiently).
Thus, if the total current in the circuit, from C to G, is sufficiently intense (which this occurs when V is sufficiently high), sufficient heat, due to passing of the electron current from G to A, will be produced to cause freedom of the electrons of the atoms ie stimulation of the right circuit to cause an electron current to flow from A to G. But this recent electron current from A to G will cancel the main electron current in the main circuit from G to A, and the result is that there will be no current practically. When there is no current in the space between G and A, there won't be any heat produced due to it, and then there won't be any stimulation to cause any electron current (in the right circuit) to flow from A to G, and then the story can be repeated, ie by increasing the voltage V, the electron current is again increased until when the heat produced due to it stimulates the voltage V' to cause an equal but opositely directed electron current to flow causing a renewed fall in the curve of I against V just at a point as far from the previous point of fall as the next point of fall.
Of course, in the real curves, each (new) peak is (a little) higher than the previous one. What presented above excluded this aspect of the experiment as an unimportant thing for the general justification of the main result of the experiment (ie existence of repeated falls in the curve at equal distances). What can be said at present for the probable cause of this effect is that by increasing the voltage there may be some electrons flowing from Cathode to Anode due to field emission. These electrons themselves make a ground current having no relation to the current produced by displacing of the valence electrons of the atoms of the gas in the tube. Only this recent current (ie one due to displacing of the valence electrons of the gas atoms) can give heat to the atoms (causing separation of their electrons if this heat is sufficiently big), because the electrons of only this current are in direct contact with the atoms. This suggestion can probably be tested by study on any alteration in the results of the experiment when we try to eliminate as many causes for the field emission as possible.
Hamid V. Ansari
My email address: ansari18109yahoocom
The contents of the book "Great mistakes of the physicists":
0 Physics without Modern Physics 1 Geomagnetic field reason 2 Compton effect is a Doppler effect 3 Deviation of light by Sun is optical 4 Stellar aberration with ether drag 5 Stern-Gerlach experiment is not quantized 6 Electrostatics mistakes; Capacitance independence from dielectric 7 Surface tension theory; Glaring mistakes 8 Logical justification of the Hall effect 9 Actuality of the electric current 10 Photoelectric effect is not quantized 11 Wrong construing of the Boltzmann factor; E=h is wrong 12 Wavy behavior of electron beams is classical 13 Electromagnetic theory without relativity 14 Cylindrical wave, wave equation, and mistakes 15 Definitions of mass and force; A critique 16 Franck-Hertz experiment is not quantized 17 A wave-based polishing theory 18 What the electric conductor is 19 Why torque on stationary bodies is zero A1 Solution to four-color problem A2 A proof for Goldbach's conjecture