Module 4 - Section 3 (Quantum Physics and Particle Physics) Flashcards
What is one photon?
One photon is one quantum of energy of electromagnetic radiation.
What is the interaction rule with a photon?
It is a one to one interaction when the photons interact with one partivle giving all or none of the energy.
What is the equation for the energy of one photon?
E = hf
-h = planks constant
-f = frequency of light
Why are electron volts used?
They are a more appropriate and suitible measure to measure the energies involved in a reaction.
What is the equation for frequency?
f = c/ λ
-c = speed of light
-λ = wavelength
What is another equation for the energy of one photon?
E = hc/λ
What is the threshold votage of an LED?
The threshold voltage is the minimum voltage needed for the current to pass across the component. This is the voltage needed to give to the electrons the same energy as a photon that is emmitted.
What is the conversion between eV and J.
1 eV = 1.6x10^-19 J
–>eV - J (times by charge of electron)
–>J - eV (divide by charge of electron)
How do you find the Planks Constant (Practical)
Set up a circuit with:
-voltmeter
-LED’s of different colours
-variable resistor
-ammeter
-power pack
Method
1. Start with the variable resistor at its maximum resistance so no current can flow.
2. Adjust the resistance so that the light just turns on hense the current just beggining to flow.
3. Record the threshold voltage (this is the voltage that just allows the LED to light up).
4. Also record the wavelegth of the colour of light that is being used.
5. Turn power pack of to allow the circuit to cool and then repeat with a different colour LED.
Then sub into the the equation:
E = hc/λ
And rearange to have h as the subjuct to find planks constant:
h = eV x λ / C
-where e is the charge of one electron
-V is the threshold voltage
What is the photoelectric effect?
The photoelectric effect is the emission of electrons (normally from a metal) caused by electromagnetic radiation (light).
What is the Work Function?
The minimum amount of energy needed for the bonds to break between the electrons and the surface of the metal in order for the electron to be emitted as a photoelectron.
What is an experiment that could demonstrate the photoelectric effect?
GOLD LEAF ELECTROSCOPE EXPERIMENT
1. A zinc plate is attached to the top of an electroscope and it is negatively charged.
2. The two gold leafs in the electroscope repel as like charges repel each other.
3. Using a UV lamp Ultra violet light is shone onto the zinc plate.
4. The packets of energy from this light (photons) causes electrons to be lost from the zinc plate via the photoelectric effect.
5. As the zinc plate looses its charge, so does the gold leafs, causing them to come back down and be together.
When are photoelectrons not emitted?
They are not emmited when the the incident radiation has a frequncy below the threshold frequency.
How does the kinetic energy of photoelectrons vary?
The kinetic energy of the photoelectrons varies with the initial frequnecy of the radiation.
When the threshold frequency is just met what is the kinetic energy?
0
What changes the amount of photoelectrons emitted per second?
The Intensity of the radiation
Why cant wave theory explain the threshold frequency?
In wave theory, even when the threshold theory is not met and is under, the electrons should gradually gain energy untill the threshold frequency is met. The particle theory is suggested her as electrons can only be released when the threshold frequncy is met or over.
What is the step by step guide to the PHOTOELECTRIC EFFECT?
- EM Radiation hits a metals surface
- The surface is bombared by photons.
- The photons then react with any free electron via a one to one reaction where 1 photon reacts with 1 electrons to release one photoelectron.
- The photoelectron gains all of the energy equal to hf
- This supports the particle like nature of EM radiation.
What is Wave Particle Duality?
When Light behaves as both a particle and a wave. A paricle due to the photoelectic effect and the gold leaf experiment and then a wave in the electron diffraction through a slit.
When Does light behave like a wave?
Light behaves like a wave in diffraction where a light been is shone through a slit and it spreads out- if it was a particle it would either pass through or not and would not spread out and carry a straight course.
When do electrons fit the wave theory?
When electrons are accelerated towards a thin graphite sheet they then pass through the Carbon atoms and then diffract as waves, producing rings on the screen at the end of the accelerator.
When do electrons fit the particle theory?
The photoelectric effect .
What is the de Broglie equation?
λ= h/p
h- planks constant
p- momentum (mass x velocity)
What is an isotope?
Elements which have the same number of protons but a different number of neutrons.
Therefore, they have the same atomic number but a different mass number.
What are the 3 forces acting on the protons and neutrons in the nucleus?
- GRAVITATIONAL FORCE
-This is attractive - STRONG NUCLEAR FORCE
-Repulsive at short distances and attractive at long distances - ELECTROSTATIC
-Repulsive between protons as they have like charges.
What is light described as?
Discrete packets of energy know as photons.
When talking about light waves what do we really mean?
All EM waves as they have the same wave speed.
If Energy is dependant on frequency what EM waves have the highest and lowest energy?
GAMMA RAYS - highest frequency = highest energy
RADIO WAVES - lowest frequency = lowest energy
What should you always to do eV?
CONVERT IT INTO JOULES!
What is all matter split into?
BOSONS
FERMIONS
What are Bosons?
Force field carrying particles, they carry a force.
What are the 4 fundamental forces and the bosons which cause them?
GRAVITY (*massless)
-theorised that it is caused by graviton
ELECTROMAGNETIC (*massless)
-caused by photon
WEAK (some mass)
-Is to do with radioactive decay caused by W boson
STRONG
-caused by gluon
What are the 2 types of Fermions?
QUARKS
LEPTONS
What are quarks?
What protons and neutrons are made of.
What are the characteristics of quarks?
They are effected by a strong nuclear force and if they are charged, experience an electromagnetic force.
What are the 6 types of Quark and the charges of these if required?
UP = +2/3
DOWN = -1/3
STRANGE = -1/3
CHARM
TOP
BOTTOM
What are Leptons?
Particles that are not affected by the strong nuclear force and are subject to the weak nuclear force.
What are 4 examples of Leptons?
NEUTRINOS
-last forever
ELECTRONS
-long life
MUONS
-very short life span
TAU
-very short life span
What is a group of Quarks called?
Hadrons
What are the 2 types of Hadrons?
Mesons
Baryons
How many quarks does a meson contain?
2 (1 quark and 1 anti-quark)
How many quarks does a baryon contain and what are the 2 types?
3
PROTON (u+u+d)
NEUTRON (u+d+d)
What’s the similarities and differences between matter and antimatter?
They have the same mass and the same properties and the only difference is that antimatter has an opposite charge.
What is the difference between a neutron and an antineutron?
The quarks within, they have the opposite quarks ie: antiquarks to make the antineutron.
