So let's look at the results of an
actual experiment where people have
taken electrons and fired them through
two slits and seeing what happens on the
screen.
So what you're seeing there are
individual blobs of white light when
electron hits the screen and when a
single electron hits the screen we see a
flash of light and so we can tell that
actually electrons are particles. So
unlike waves they're particles, and
that's what we'd expect to see if we
were sending a very small number of
particles through who wouldn't see a big
fuzzy blob, what we'd see is individual
strikes. If it had been a wave than we
would have seen a weak interference
pattern so it would have been those
bright and dark interference fringes
across our entire screen, but very very
weak. And instead we're seeing these
blobs so alright they're particles. But
you'll notice that as the speed of the
movie increases and we see more and more
of these blobs then something rather
strange is happening  - we're seeing that
those blobs are more likely to appear.
The electrons are more likely to strike
where the bright fringes of the
interference pattern would have been if
it had been a wave, and they're much less
likely to strike where the dark fringes
of the interference pattern would have
been if they're a wave. And it's what
we've discovered is that both of these
theories the particle theory and the
wave theory are wrong. If the particle
theory had been right then we would have
got these blobs all right but they would
have on average not made some lovely
interference pattern, they would have
just ended up making this big smushed out
blob. And if the wave theory had been
exactly right we wouldn't have expected to
see blobs at all. We were expected to see
a weaker and weaker version of that
interference pattern. But instead we need
a hybrid theory that could explain both
the blobs appearing and the eventually
interference pattern. And that hybrid
theory is what we now call quantum
mechanics.
