when light encounters a mirror it gets
reflected. Why? Because the photons, the
particles by which light is consisted
of, crash with a massive solid. And that
causes the direction of the photons
velocity to get opposed. Exactly like a
basketball bouncing.
Why is the sky blue
and the sunset red? Because light is a
wave and when the white light from the
Sun interacts with the atmosphere, the
blue light gets scattered way more than
red light does. So at noon the sky is
blue because you are seeing all the blue
light the person who is watching the
sunset doesn't see. At sunset light
passes through so much atmosphere the
possibility of some blue light traveling
that far is very small. And if you
subtract the blue light from the white
light you get just the Orannge-Red.
 
How does the photoelectric effect work?
When photons with a specific frequency hit
the electrons of an atom, they transfer
their energy to them. And if the energy
is enough the electrons can escape the
atom. So the material gets positively
charged since some electrons have
escaped.
Answers like these to questions
like these have their purpose and the
serve us good sometimes but as people
start to dig deeper to more and more
advanced physics, these answers serve a
same problem. They make people think that
an either/or answer to this question
(is like a wave or made out of particles after all)
exists
or
even worse
that we haven't answered it yet.
When neither that is true.
Let me explain.
The correctway to answer this question is:
Light is the collection of excitations in the
photon field.
So anything like getting reflected of a mirror,
getting scattered from earth's atmosphere,
give energy to an electron
Bend when entering water and so and so forth,
can be explained just by
considering light to be excitations in
the photon field and behaving according
to quantum field theory.
Done!
it's no mystery anymore
same goes for the electrons
it's true that some phenomena
can be explained by the particle nature
and some others by the wave nature but
absolutely all of them can be explained
by the excitation in the electron field nature
the roots of quantum field theory
have something to do with waves and
Newtonian particles though, as well as
special relativity.
In classical physics
a particle is something which has no
size and it obeys Newton's laws of motion
a wave on the other hand in
classical physics. Diffracts when it
passes through a slit,
gets reflected when it counters a surface
refracts when it changes the medium it passes through
and it interferes with other waves
phenomena like the photoelectric
effect and the ultraviolet catastrophe
could only be explained by considering
light to be a stream of particles in the past.
And phenomenon like interference
pattern from a double slit could only be
explained by considering line to be a wave
and for this reason physicists were
puzzled about the double nature of light
also from 1927 and beyond thanks to the
work of Lewis de broglie, we know that
apart from light electrons and other
small particles have a wave particle
like behavior
hence the term wave particle duality was born.
This led to the inception of
quantum mechanics.
Quantum mechanics
could explain all of the above phenomena,
So it was superior to both light
is a particle theory and the light is
a wave theory
quantum mechanics still
describe light electrons and everything
as particles
but instead of obeying Newton's laws of
motion they obeyed Heisenberg's
uncertainty principle.
They do not have a
specific position and velocity.
Pauli's exclusion principle (fermions cannot have
the same quantum state)
the superposition principle
they could be in multiple
positions at the same time
Schrödinger equation
and others
properties which weren't present for particles with
the Newtonian term, in which they had a
specific position velocity and it was
only one.
Quantum mechanics did fix many
of our problems which were present but
there was one big problem.
They did not
take into account Einstein's relativity
so we tried fixing that problem and we
partly succeeded. We managed to merge
quantum mechanics with special
relativity and that's what we call
quantum field theory.
Quantum field theory
changed the interpretation of
fundamental particles to excitations in fields.
Very loosely speaking every
fundamental particle has its own field
which exists everywhere in the universe
but has a zero value. Except where a
particle would be. Where the field has a
high value. What we call excitation
despite our efforts we didn't and we
still haven't merged quantum field
theory with general relativity.
So when I
said quantum field theory can explain
everything. Well I meant almost
everything. It still lacks features like
gravity, due to the incompatibility with
general relativity,
dark matter
dark energy
matter with antimatter asymmetry
and neutrino oscillations.
And this is
where today's research is focused on.
So keep learning physics and you may
contribute to this task.
