Word Wall:
Quantum Mechanics: a division of mechanics that looks into
the math behind the motion/relationships of subatomic particles (ex: electrons,
protons, neutrons).
Quarks: an elementary particle that makes up matter, when
combined they can form ‘composite particles’ an example being protons and neutrons
– they cannot be found in isolation.
Photoelectric effect: metals will emit electrons if you shine light on them (the electrons that are produced are labelled
photo electrons)
Planck’s constant: 6.626 x 10-34 J s
Photons: an elementary or quantic particle, made of energy
Wave – particle duality:
Alright, so ready to have your mind boggled? Let’s look at
our friend quantum mechanics who so confusingly explains the fact that quantic
entities (like quarks) will experience both the properties of waves and the
properties of particles. This is basically challenging the whole idea of the classical
definitions of particles and waves entwining the two. The scientist Louis de Broglie began the research
creating his hypothesis in University all about the funny movement of particles
and how their behaviour was no longer as linear as what was originally thought.
The theory was later named the Broglie-Bohm theory. If we are going to talk
about De Brogie then we might as well know how he went stated that
not only light has the properties of waves, his equation was something along
the lines of wavelength = Planck’s constant/momentum; this equation stemmed
from Albert Einstein’s research into what is today called the photoelectric
effect. De Broglie's theory was
proved for electrons using experimentation and observations done by George
Paget Thomson and Clinton Joseph Davisson who both at separate locations
passed a beam of electron through a device to see the interference pattern
(which showed the conclusions that De Broglie had predicted – that the electrons act
both as waves and particles). Now, you may be wondering what I mean by “acting
as waves and particles” so to explain this I have found a great illustration which
actually shows the experiment I will talk about in the next paragraph. There
have been other experiments done to look at atoms and molecules
which all describe the same results – sometimes they act as waves, sometimes
they act as particles.
To illustrate this theory we will look closer into one of
the many experiments done to prove it, an experiment done by Thomas Young in
the year 1801. The experiment was called The
Double Slit Experiment. The experiment starts with the idea that
light is made of photons travelling in electromagnetic waves; however once these
waves pass through two slits there become two sets of waves until
they are to hit the screen where the wave field fades away and the photons
reappear – the collapse of waves into a small singular point. The set up for
this experiment is obviously not too hard to comprehend; it involves a laser
beam, a pierced plate with two parallel slits cut through it and a screen to
make the observations of the interference pattern of the light. What is a photon and how is it made? Time
for a bit of grade ten chemistry. Atoms have orbits with electrons that circle around the nucleus in specific patterns. Photons are produced by the energizing of electrons that orbit the nucleus of an atom. The electrons are pushed to a greater orbit and then they fall back down to their original orbit releasing energy (they go from the higher energy orbit to the lower energy orbit). The photons that are produced have the colour and frequency
of the distance that the electron has fallen. The Double Slit Experiment can be done by looking at electrons or even entire atoms which
can be fired at a double slit and observed on the screen (refer to image above) – the observations
prove the duality of waves and particles. The weirdest part
is when we look at the relational interpretation which explains that a singular
electron can actually appear to be at both slits at the same time – this is
explained by the relationships between the points on the screen and the slit
locations!
I do not think that I have given Einstein enough credit since he did embrace the idea of wave –particle duality even when many humans
tried to deny the possibility. I started talking about the photoelectric effect
and Einstein’s contributions however I did not mention that good old Einstein
was a tricky man and in order to make his theories work he seemed to have a
hard time picking: is light a wave or a particle and instead decided to choose
both. By this I mean he would use the property that best suited his science and
observations at the time. For the photoelectric effect he chose to think of
light as a photon (a particle) and later when explaining the idea of special
relativity (which we will talk about in a future post) he labelled light as
having the properties of waves. In modern times scientists seem to agree that
light is weird and has both the properties of particles and waves, like
Einstein believed way back in 1905.
If you still cannot grasp this strange concept try listening to Dr. Quantum in this video where the double slit experiment is shown and explained in detail.
Websites Consulted:
https://www.oist.jp/sites/default/files/photos/Doubleslitexperiment-SM.jpghttps://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality https://en.wikipedia.org/wiki/Photoelectric_effect
https://en.wikipedia.org/wiki/Quark
http://www.merriam-webster.com/dictionary/quantum%20mechanics
https://en.wikipedia.org/wiki/Double-slit_experiment
http://science.howstuffworks.com/light9.htm
https://www.youtube.com/watch?v=DfPeprQ7oGc
