What if I told you that the angle of
reflection is not always equal to the
angle of incidence. Today we answer this questions in just three minutes by
understanding the basics of Quantum
Electrodynamics. Quantum means energy and
Electrodynamics means interaction of
electric current with the magnetic field
these phenomenons can be explained by
the interaction of electrons and photons
or rather virtual photons because they do
not really exist. They acquire their mass from
energy, they interact, and they disappear. let's
say we want a photon to travel from a
light bulb to a light detector. Now we
start the stopwatch at the time the
photon is emitted from the light bulb
and we stop the stopwatch at the time
it is detected by the light detector
If we do this consistently for the
different paths a photon can take to reach
the light detector, then we will find
surprising observations. If we connect
all the stopwatch needles from head to
tail and then finally connect the head
of the first needle to the tail of the
last then we can find the total
probability of that event happening. To
understand why light takes the path where the
angle of incidence is equal to the angle of
reflection, we'll see an analogy. Let's
say it's NBA championship match and you
have the ball in hand. All your team players
are covered up and the opposition team
is gathered at the center. Which path
would you take to basket the ball? The
total probability of an event happening can
be found by summing up the probability
of different paths. The stopwatch needles
we just discussed are nothing but
vectors that have magnitude and
direction and when they were calculated
for the paths at extreme ends then the
direction of the needles was opposite so
they got canceled and the direction of
the path in the centre was similar so
they got add up. This is the reason
why you and even light is more likely to
take the center path where the angle of
reflection is equal to the angle of
incidence and you also can score a
basket! Tomonaga and Schwinger gave us
intimidating and complex mathematical
equations to account for the interactions
between these electrons
and photons but Feynman, a great
explainer and a great bongo player
for that matter made these equations
into cool pictorials
now known as the Feynman diagrams. These
diagrams are as popular amongst
the scientists as Feynman was amongst
the ladies. Now to understand these
diagrams we must know that the movement
of an electron is given through a
straight line and that of a photon through wiggly
line. In these Feynman diagrams, the actions
spots are places where the electrons
emit or absorb the photons. These action
spots more or less decide the complexity
of the diagram. As the complexity of the
diagram increases, its probability of
contributing to the actual path
decreases tremendously. This is no
surprise why it is known as one of the
most precise and consistent theories in
the history of mankind and well the Jewel of Modern Physics.
