At the beginning of the experiment, we can see
that bright spots begin to appear here and there at random
positions. These are electrons.
Electrons are detected one by one as particles. As far as
these micrographs show, you can be confident that electrons
are particles. These electrons were accelerated to 50,000 V,
and therefore the speed is about 40 % of the speed of the
light, i. e., it is 120,000 km/second. These electrons can
go around the earth three times in a second. So, they pass
through a one-meter-long electron microscope in
1/100,000,000 of a second. It is all right to think that
each electron is detected in an instant after it is emitted.
Interference fringes are produced only when two electrons
pass through both sides of the electron biprism
simultaneously. If there were two electrons in the
microscope at the same time, such interference might happen.
But this cannot occur, because there is no more than one
electron in the microscope at one time, since only 10
electrons are emitted per second.
Please keep watching the experiment a little longer. When a
large number of electrons is accumulated, something like
regular fringes begin to appear in the perpendicular
direction. Clear interference fringes can
be seen in the last scene of the experiment after 20 minutes.
It should also be noted that the fringes are
made up of bright spots, each of which records the detection
of an electron.
