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Photons: Light Waves Behaving as Particles (Photoelectric Effect: Light…
Photons: Light Waves Behaving as Particles
Photoelectric Effect: Light absorbed as photons
Light is absorbed as photons
Light is absorbed as bundles of ""particles
Expectations and Results
Expectations
Using the wave model we'd expect:
Independent of \(\lambda\)
If we need intensity to push off electrons the wavelength of the light doesn't matter
Delay Time
If we had a low intensity it would take us some time to gain enough energy to push the electron off
\(V_0 \alpha I\)
If we have a high intensity light coming in, it would take more energy to repel the electrons
Results
Photoelectric effect is dependent on \(\lambda\)
After a certain wavelength we can't push electrons no matter how high the intensity is
There is no delay to push off electrons no matter how faint the intensity is
\(E\alpha f\)
Intensity has no effect on the voltage but frequency does
intensity only affects current
Explanation
\(E=hf\)
All-or-nothing
Einstein imagines photons (bundles of particles) going directly to a singular electron
If the electron receives enough energy then it has the energy to be pushed otherwise it doesn't move
This explains
Why there's no delay time
Either it has the proper amount of energy or not
Procedure
Cathode
-Negatively charged
Anode
-Positively charged
The opposite charges causes a potential difference
When the Electric field is oriented so that the electrons are heading towards the Anode we consider this \(v_{max}\)
If we decided to reverse the electric field this would would make it harder for the electrons to go to the anode. At some point no more electrons hit the anode
Since the electrons can't move to the anode the circuit can't be completed meaning current is 0
But this builds up the potential difference of the battery
We consider the Voltage required to cause no electrons to reach the anode the
Stopping Potential
1 more item...
Phenomena
With enough energy light is able to push electrons off a surface
The interesting part is that only energy at specific points allows the electrons to be pushed
This shows that the electrons can only be pushed at specific points
Energy of light is becoming transferred to Kinetic Energy of electrons
Questions
If all or nothing where does the energy of the nothing go
shows that a huge number of photons leave
the laser pointer each second, each of which has an infinitesimal
amount of energy. Hence the discreteness of the photons isn’t
noticed, and the radiated energy appears to be a continuous flow
X-Ray production: Light emitted as photons
When we bombard an object with particles we'll emit radiation
