Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Physics > Particle > Flashcards

Particle Flashcards

(76 cards)

Start Studying
1
Q

Photoelectric effect

A

Photoelectric radiation releases light as photons with varying frequencies.
Frequencies above threshold frequency cause electron emission, photoelectrons.
Different metals have different threshold frequencies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How can light be portrayed in relation to electrons?

A

Electromagnetic waves travel as packets of energy called photons
If frequency above threshold frequency, intensity increases electron emission
Each electron can absorb a single photon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Em waves as particles

A

There is no time delay despite intensity
Particle theory suggests eventually any wave should cause electron emission, but any below threshold frequency do not
Increasing intensity should effect all waves, but if below threshold frequency they don’t

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Stopping potential

A

Stopping potential is the potential difference you would need to apply across the metal in order to stop the electrons with max KE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Work function

A

Minimum energy required to free an electron from surface of a metal (to overcome metallic bond)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Threshold frequency

A

Minimum frequency is the minimum frequency of wave needed to free an electron from surface of metal. Different for each metal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Excitation

A

Excitation occurs when an electron collided with a photon or electron, absorbing energy. This raises the electrons energy level but does not free it from the atom. Immediately the electron then drops back to its original energy level (de-excitation). This re-emits the energy as photons. The electron won’t absorb energy unless the electron or photon has the exact amount of energy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Ionisation

A

An electron absorbs a photon or an electron with a specific energy. If this is greater then the threshold frequency then the electron will be freed from the surface of the electron known as ionisation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Changing energy levels equation

A

hf=E1+E2 or E=E1+E2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Energy levels descriotion

A

Ground state = lowest
Ionisation = highest
Energy levels are not evenly spaced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is fluorescence

A

A high voltage is created, accelerating free electrons through the tube.
Electrons collide with mercury atoms causing some electrons to ionise but most to excite emitting photons in the UV range. The process repeats.
The fluorescent coating lining the tube absorbs this UV light causing the atoms within it to become excited and then de-excite, the photons are then re-emitted in the visible light range.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is an electron volt and its value?

A

The energy gained by an electron when passing through 1 volt of potential difference.
1.6x10*-19

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How can light be seen as a wave?

A

Light diffracts

Light interferes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How can light be seen as a particle?

A

Photoelectric effect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How can an electron be seen as a particle?

A

Mass

Charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Electrons as a wave

A

Electron diffraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

De Broglie wavelength equation

A

Wavelength=h/mv

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Meaning of de broglies equation

A

As momentum increases, wavelength decreases and therefore so does the amount of diffraction.
This decreases the gap between concentric rings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Four fundamental forces

A

Weak
Strong
Gravity
Electromagnetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a lepton

A

Doesn’t respond to strong nuclear force

Electron/muon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is a hadron

A

Particle that react to the strong nuclear force
Split into baryons and mesons
Have a quark structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How many quarks does a meson have and how many does a baryon have

A

Mesons have 2 (quark and antiquark pair)

Baryons have 3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

When is strangeness not conserved?

A

For weak interactions because a s quark may need to decay into an u quark for example. It can only change one at a time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is always conserved in interactions?

A 
Momentum
Energy
Charge
Lepton number
Baryon number
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is the strong nuclear force
Force that keeps nucleus stable by counteracting electrostatic force
26
What is the range of the strong nuclear force
0.5-3fm Below 0.5fm it is repulsive Above 3fm it is negligible
27
What makes nuclei unstable
Too many protons, neutrons or both
28
How do nuclei with too many nucleons decay?
Alpha decay
29
How do nuclei with too many neutrons decay?
Beta decay (neutron decays to a proton via weak interaction)
30
How was the neutrino discovered?
Energy before the reaction was not equal to the energy after, so a particle with no charge and negligible mass must carry it away
31
What is beta minus decay?
Decay of a neutron into a proton via the weak interaction. A down quark changes to an up An electron and anti electron neutrino are released
32
What is beta plus decay?
A proton decaying into a neutron via weak interaction. An up quark changes into a down. A positron and an electron neutrino are released
33
What is annihilation?
A particle and its corresponding antiparticle interfere. There masses convert into kinetic energy in the form of gamma photons. Thee go in opposite directions to conserve momentum
34
What is pair production?
A gamma ray photon converts into a particle and it’s antiparticle The photon must have at least the energy of the particles’ two rest masses
35
What is the exchange particle of the electromagnetic force
A virtual photo
36
Where are muons found and what are they?
In cosmic rays in the atmosphere | Leptons which are heavier than electrons but can break down into electrons and other particles
37
What is the exchange particle of the weak interaction?
W+ or W- boson
38
When does the weak interaction occur?
When there is a change in quark structure | Typically in decays
39
What are the two main types of meson and which is linked to strangeness?
``` Pion Kaon (strangeness) ```
40
What is the exchange particle of the strong interaction?
Pion
41
What is significant about the proton?
It is the only stable baryon | All baryons will eventually decay into a proton
42
What is responsible for the production of a strange particle and the decay?
Strong nuclear interaction (production) | Weak nuclear interaction (decay) can change the strangeness by 0, -1, +1
43
Why does a photon need to be of a minimum frequency to liberate an electron?
Energy is determined by frequency. An electron must have energy greater than the work function to be freed
44
Photoelectric equation
hf=Ek+ ø
45
What can be used as evidence of energy levels?
Line emission and absorption spectra Lines appear at discrete levels proving that a light photon of specific frequency has been absorbed or emitted This shows electrons can only absorb photons of exact frequency to move between energy levels
46
What does a muon decay into?
Electron, electron anti neutrino, muon neutrino
47
What is meant by a free hadron?
They are not in atoms
48
What happens to free neutrons?
They are unstable so decay into protons via the weak interaction
49
What does a kaon decay into?
Pions
50
What is specific charge?
Charge per unit mass
51
Use of isotopes
Carbon 14 for carbon dating, they can detect the age of a previously living thing as all living things have same amount of carbon 14 to start with. We know the half life so by calculating percentage left we can age the thing.
52
Isotopes of hydrogen
Deuterium (2 neutrons) Tritium (3 neutrons)
53
Exchange particle for beta minus decay
W-
54
Exchange particle for beta plus decay
W+
55
What caused finding of neutrino
Energy was not conserved in equations so there must be another particle
56
How does EM radiation travel
packets of energy called photons
57
exchange particle of electron capture
W+
58
Exchange particle of electron-proton collision
W-
59
What happens in electron capture?
Proton absorbs an electron as it is heavier decaying it into a neutron. An electron neutrino is also released
60
What is different between electron capture and electron-proton collisions?
A minus boson for electron-proton collisions. Other than that they are identical
61
Use of electromagnetic force
Binds electrons to atoms Holds protons apart Responsible for repulsion
62
Use of gravitational force
Only affects particles with a large mass
63
What must be conserved in interactions?
Energy Momentum charge baryon number electron lepton number muon lepton number strangeness (except in decays)
64
Analogy to understand exchange particles
If you throw a ball to someone, momentum makes them move back So exchange particles carry momentum and energy
65
How are scientific theories validated?
physicists hypothesise experiments done and repeated to reduce experimental uncertainty Theory validated
66
Difficulties of validating theories?
Involves large groups of scientists and engineers due to expense of machinery as well as complexity of experiments
67
What is a spark counter and how does it work?
Detects highly ionising alpha particles. Metal gauze placed near to a thin wire. A voltage is applied causing the ionisation to create sparks which are visible to naked eye
68
What is a geiger muller and how does it work?
Detects alpha particles. Alpha particles enter the tube causing the gas in detector to ionise. These ions are attracted to anode creating a pulse of current between anode and cathode which is seen as a count
69
How does a cloud chamber show alpha particle interactions?
Alpha particles hurtle through cold, wet air, detaching an electron from atom after atom. These leaves a trail of ions (condensation).
70
Equation for speed of an electron
square root of 2eV/m
71
Demonstration of photoelectric effect
when electroscope is given a negative charge the gold leaf rises and stays up. If UV is directed at the zinc plate above the leaf begins to fall, discharging it. If UV is removed the leaf goes up again.
72
Describe how line spectra show different energy levels of electrons
Shine fluorescent light at diffraction grating. This creates a line spectra as the photons emitted correspond to a specific energy level shown on the spectra as a coloured line.
73
How can line absorption show different energy levels?
Pass white light through a cool gas and ionisation will create photons not in the visible light range creating a dark line on the spectrum.
74
How does an electron diffraction tube work?
Electron gun accelerates electrons to high potential (around 5000V). This is fired at a graphite film causing electrons to diffract from gaps between carbon atoms. This produces a circular pattern on fluorescent screen.
75
How does voltage of electron diffraction tube vary with energy and velocity
as voltage inceases the energy and speed increases
76
How does scientific knowledge change?
Experimental evidence Peer reviewed

Physics (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions