Transcript he proved that light was also made up of particles!

The Photoelectric Effect
Story Time
Once upon a time 
A bunch of old dudes were arguing about whether the
nature of light was founded in being a particle or a wave.
Light is a
wave Bro!
It’s a particle
– and I’m
not your
Bro!
Eventually they all decided it was a wave

It refracted, reflected, diffracted, and did all the other
things waves do!
But in their hubris, they forgot something…
An Event called….
 The
Ultraviolet Catastrophe!!!
What’s That!!!???
The ultraviolet catastrophe

When a UV light was shined on a piece of metal – it
releases a significantly larger glow and a voltage(energy)
than any other light, and
their math didn’t add up.

They couldn’t explain it – because light was a wave and the
only things that could produce electricity were electrons –
which are tiny particles of matter. They were certain that
light was not made of matter – it couldn’t be!
With such a great event contradicting
that pure wave statement

They did what any great societies have historically done
during a time where comfortable knowledge and science
clash!!!
Unable to explain it…

They pretty much dismissed it and moved on…
But then…

Some guy was like, hold on.
We can’t ignore
this...We must do
Science!
So then he did some science…

And came up with a the discovery of his time(1905)
YEAH! SCIENCE!

It could explain how light could produce electricity
through metals – and then some!
But who discovered it?

There were a lot of people and experiments trying to
explain how light could produce electricity– but one man
figured out how to explain it the best.

Guesses anyone?
Hint:
Old Dead White Guy
Crazy Hair
Mustache
Name Rhymes with Schmalbert Schmeinstein….



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That’s right!

This Guy – Albert Einstein

Despite what most people
know about his
contributions to the
scientific world – aka
working on the atom bomb,
theory of relativity –the
photoelectric effect is
probably his greatest
discovery!
Such Science. Much Glory. Wow.

He won a nobel prize in
science in 1921 for his
explanation of the
discovery of the
PHOTOELECTRIC EFFECT

As a matter of fact, it was
such a strongly founded
idea it was basically the
foundation for the study of
quantum physics!
First off…What is the PhotoElectric Effect?

The photoelectric effect occurs when a wave pack of high
energy Photons strike a metal surface and repel Electrons
from the surface.

Note: the photons
have to overcome a
frequency threshold
of the electrons from
the metal.
What is the PhotoElectric Effect?


Photons release Electrons from metals
PhotoElectric Effect
What’s going on, on the surface?

Photons have to have a high enough energy/frequency to
displace the electrons
What was the big deal?


It wasn’t just that he explained how electricity could be
produced by light.
It was that , AND he proved that light was also made up of
particles!
He said that extra glow, the extra energy

were tiny particles traveled in waves he called “quanta”,
that were forcibly knocking off electrons from surface
of the metal.

He mathematically calculated
that if the “quanta” has a high
enough frequency(high energy),
then the it would displace
the electron from the metal.
We know that type of quanta today as

PHOTONS – massless particles of pure energy!

The issues and solution:
Waves cannot carry matter, only energy. A photon has no
mass, and is pure energy – therefore a wave can carry
photons.


Only particles can interact with particles, so electrons can
interact with photons.
Such Science. Much Glory. Wow.

As a matter of fact, it was
such a strongly founded
idea it was basically the
foundation for the study of
quantum physics!

Quantum physics has its
own set of rules, and
doesn’t have to work in the
classical sense of physics!
IT FINALLY PUT AN END TO THE
DEBATE OF WAVE VS PARTICLE

EM waves have properties of both waves and particles.

In the world of physics we call this –
WAVE-PARTICLE DUALITY

Who cares?

You should – this century and all it technological marvels
exist because of this discovery!

Digital Cameras
Remote Controls
Cell Phones
Televisions
Smoke Detectors
Burglar Alarms
Automatic Sliding Doors!!!!!!!!!!!!!!
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