Particles and waves Flashcards
A charged particle in an electric field experiences what?
A force
(and therefore because f=ma it will accelerate)
Which direction do field lines run for a charged particle or for charged plates?
Arrow goes from +ve charge to -ve charge
(or outwards from a +ve point charge, inwards to a -ve point charge)
For a +ve charge in a magnetic field how do you work out which direction it will move?
Use left hand rule
- thuMb is direction it will Move
- First finger is direction of magnetic Field
- seCond finger is direction positive Charge is originally going
for negative charges swap to right hand
What is meant by a fundamental particle?
A particle that cannot be subdivided into other particles
How many fundamental particles of matter are there?
12
6 leptons
6 quarks
In the standard model what type of particle is an electron?
A lepton
(and also a fermion)
In the standard model what sort of particle is a proton?
A baryon - it is made of 3 quarks
(and it is also a hadron and a fermion)
In the standard model what sort of particle is a neutron?
A baryon - it is made of 3 quarks
(and it is also a hadron and a fermion)
What is the force mediating particle for gravity?
A graviton
What is the force mediating particle for the electromagnetic force?
A photon
What is the force mediating particle for the strong nuclear force?
A gluon
What is the force mediating particle for the weak nuclear force?
W and Z bosons
What’s the difference between the strong nuclear force and the weak nuclear force
Strong nuclear force binds protons and neutrons in the nucleus (and binds quarks in hadrons)
Weak nuclear force is responsible for radioactive decay
What is the general term for a particle made up of quarks?
A hadron
there are 2 types of hadron - a baryon and a meson
High-energy collisions between electrons and nucleons, carried out in particle accelerators give the evidence that what exists?
quarks
What is an antiparticle?
And what symbol represents it?
Every particle has an antiparticle that has SAME mass and OPPOSITE charge
A line over the top of the symbol name means antiparticle
How do we know antimatter exists?
Because if particles are annihilated in a particle accelerator then energy is given off
What gave the first evidence of the neutrino?
Beta decay
What happens in beta decay?
- a proton in an atom changes to a neutron
- an electron is emitted
- a neutrino is emitted
What is the name of a particle made up of a quark-antiquark pair?
A meson
What’s the name of a particle made up of 3 quarks
a baryon
If two small nuclei combine to make a larger nucleus what type of nuclear reaction is this?
Fusion
2 Unite so fUsion
If one large nucleus splits to make two smaller nuclei what type of nuclear reaction is this?
Fission
2 splIt so fIssion
What type of nuclear reaction takes place in the a nuclear power station?
fission
Why do nuclear fusion reactors need magnetic fields
Because you need a high temperature (plasma)
Containers would melt in such high temperatures
What is the definition of irradiance
The power per unit area incident on a surface.
use the formula sheet I=P/A to help you remember this!
When can you use this equation to calculate the irradiance?
I=k/(r squared)
If you have a point source
a point source sends light in every direction from a point
remember a laser is NOT a point source
What is the name of the effect which is evidence for the particle nature of light.
the photoelectric effect
What is the name of the effect which is evidence for the wave nature of light.
interference
Explain what is meant by a coherent wave?
A coherent wave has a constant phase relationship (and has the same frequency, wavelength and velocity
State 3 facts about the Bohr model of the atom
Any 3 of these
* an atom has a small, positively charged central nucleus
* electrons orbit at specific fixed distances from the nucleus and electrons are not allowed to orbit in the space between these specific fixed orbits.
* each of these electron orbits has an energy level associated with it.
How is a line in an emission line spectrum produced?
When an electron in a higher energy state relaxes to a lower energy state and gives off a photon.
The energy of the photon gives the frequency of the line from E=hf
How is a line in an absorption line spectrum produced?
If a photon has a frequencies/wavelength giving an energy (E=hf) that is the same as the energy gap between electron energy bands
It is absorbed into the atom and transfers its energy to the electron which moves to a higher energy state
In the bohr model - if you had these energy levels how many lines would be produced?
E3_____
E2_____
E1_____
E0_____
**6 lines
**
allowed transitions are
E3 to E0
E2 to E0
E1 to E0
E3 to E1
E2 to E1
E3 to E2
What is the name of the lowest energy level in the Bohr model of the atom?
Ground state
Given symbol E0
In the Bohr model, if an electron gains energy it can move to a higher energy level.
We call this state what?
Excited state
In the Bohr model of an atom, if the electron gains enough energy to completely remove it from the atom it is said to be in what state?
Ionisation state
Why do we have different colours in a line spectrum?
Because different electron transitions release photons with different energy,
These different energies mean different frequencies (and wavelength) because E=hf.
The wavelength/frequency determines the colour.
The data sheet has the wavelengths for the line spectrum of hydrogen
How do I find the charge of a proton?
The charge on a proton is the same magnitude as the charge of an electron
It’s on the data sheet as the charge of an electron
electron charge is -ve,
proton charge is +ve
What is the definition of the critical angle?
The angle of incidence such that the angle of refraction is 90 degrees
In the equation
n= sin (θ 1) / sin (θ 2)
how do you know which to use for θ 1 and θ 2?
θ 1 is always the angle in air
it doesn’t matter if it’s the angle of incidence or the angle of refraction
In the photo electric effect - what happens?
When you shine light on a material, if a photon of light has enough energy (more than the work function) it knocks an electron out of it’s orbit and it becomes a free electron (called a photo-electron)
photo - photon, electric - electron
What’s the symbol for the work function?
there is no symbol!
Work function =hf0
this is in the equation Ek=hf-hf0
What is the symbol for threshold frequency?
f0
For the photoelectric effect, if you have a graph of
kinetic energy of electrons against
frequency of the light
how can you work out the threshold frequency?
It’s the point where the straight line crosses the x axis
When does the photo electric effect take place?
If the energy of the light incident on the material is greater than the work function
E > hf0
Or when the frequency of the light is greater than the threshold frequency
f>f0
Explain in terms of waves how a minimum in an interference pattern is observed?
A crest/peak of a wave meets a trough of a wave
Explain in terms of waves how a maximum in an interference pattern is observed?
A crest/peak of a wave meets a crest/peak of a wave
Explain how the dark lines in the spectrum of sunlight are produced.
Photons of certain energies/frequencies are absorbed
In the sun’s atmosphere
Explain why a spectrum is produced in a glass prism.
Different frequencies/colours have
different refractive indices
so are refracted through different angles
Explain why energy is released in a fusion/fission reaction.
because mass is converted to energy
E=mc^2. Mass afterwards is less than mass before
Explain why the photoelectric effect provides evidence for the particle nature of light?
Each photon contains a fixed/discrete
amount of energy
Each photon removes one electron
Explain why particles such as leptons and quarks are known as
fundamental particles.
Fundamental particles (Leptons and quarks) cannot be subdivided
Explain why a fusion reaction is hard to sustain in a nuclear reactor
The particles need to be at a very high temperature
