CH110 Study Guide - Final Guide: Radiant Intensity, Electric Field, Photon
It is instructive to discuss two known
experiments that were regarded as impressive
evidence for the corpuscular nature of
electromagnetic radiation. In the experiment by
Joffé and Dobronrawov [22], a small particle of
dust suspended in an electric field was exposed
to a very faint flux of X-rays. Every 30 minutes
on the average a photoelectric event occurred
causing the particle to wince because of
emission of an electron, the wince being
observed visually. When discussing this
experiment, one asserts that the experiment can
be explained only if one invokes the concept of
a particle-like photon that gives energy to the
electron instantaneously, otherwise it is quite
incomprehensible why only one out of a wealth
of electrons in the particle accumulates energy
during 30 minutes in order to be able to escape
from the particle when the energy suffices for
this. If one leans upon the above presented
undulatory point of view, does no electron in the
particle accumulate energy during half an hour.
On the average every half-hour there occurs
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resonance interaction of one of the electrons
with the incident electromagnetic wave (the
probability of the interaction being proportional
to the intensity of the wave according to (5.2)
was very low in that experiment). The electron
sucks in the whole of the energy almost
instantaneously (more precisely, with the speed
of light) and escapes from the particle. All of
this looks as if a particle has suddenly struck the
electron and knocked it out of the metal.
Another experiment, by Bothe [23], was in
essence as follows. A metallic foil was exposed
to X-rays and emitted secondary X-rays owing
to X-ray fluorescence. The foil was placed
between two X-ray counters, so that the
counters received the X-rays from the opposite
sides of the foil. If atoms of the foil emitted
spherical X-ray waves, the counters should
come into action simultaneously. In the
experiment, however, the counters gave
readings incoherently with each other. One
concluded from this that the X-rays were made
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Document Summary
It is instructive to discuss two known experiments that were regarded as impressive evidence for the corpuscular nature of electromagnetic radiation. Joffe and dobronrawov [22], a small particle of dust suspended in an electric field was exposed to a very faint flux of x-rays. Every 30 minutes on the average a photoelectric event occurred causing the particle to wince because of emission of an electron, the wince being observed visually. If one leans upon the above presented undulatory point of view, does no electron in the particle accumulate energy during half an hour. The electron sucks in the whole of the energy almost instantaneously (more precisely, with the speed of light) and escapes from the particle. All of this looks as if a particle has suddenly struck the electron and knocked it out of the metal. Another experiment, by bothe [23], was in essence as follows.
