Particles and Waves Flashcards
What is the ionisation level?
This is the energy needed by an electron to leave the atom altogether.
What is beta (minus) decay?
Beta (minus) decay is when a neutron decays into a proton releasing an electron and an antineutrino.
What will a stationary charge create?
An electric field
When will a gold leaf electroscope discharge?
- It must be negatively charged
- It must have a zinc plate
- Ultraviolet light of a high enough frequency must be shone on the plate
- When the frequency of the ultraviolet light is above the threshold frequency
What information do you get from a chemical symbol, such as the one shown below?
Top number = Mass Number = number of protons and neutrons in the nucleus.
Bottom Number = Atomic Number = number of protons in the nucleus.
The letters are the chemical symbol which can be found on the periodic table.
A triangular prism can be used to split white light into a spectrum. Why does this occur?
Different frequencies/colours have different refractive indices.
What will increase the amount of diffraction?
- Longer wavelengths diffract more
- Narrower gaps cause more diffraction
When is the energy of the ionisation level?
0 Joules
What type of spectrum is this?
Line absorption spectrum
What is the period of a wave?
The time it takes one wave to pass a point.
What are the names of the 6 types of Quarks?
- Up
- Down
- Charm
- Strange
- Top
- Bottom
In physics what is meant by a field?
It is the region where an object experiences a force.
What is meant by fission?
Fission is when a nucleus of a large mass number splits into two or more nuclei of smaller mass numbers.
What type of spectrum is this?
Continuous spectrum
What is the test for a wave?
If it can cause interference.
When will total internal reflection occur?
- Incident light must arrive at the boundary at an angle greater than the critical angle
- Occurs when light tries to pass from an optically dense material to a less dense material (e.g. from glass to air)
What is the critical angle?
The angle of incidence (within a material) that gives an angle of refraction of ninety degrees.
If a spectral line is bright - what des this tell you?
More electrons are making that energy level transition producing more photons of light with the same frequency.
What will a moving charge experience in a magnetic field?
A force
What is the definition for electric field strength?
The electric force per unit charge acting at a point in the field.
Describe the electric field between a positive charge and a negative charge.
Field lines run from positive towards negative.
What is a fundamental particle?
A fundamental particle is one that cannot be broken down into any sub particles.
What represents a magnetic field going ‘into the page’?
A cross
What will a moving charge create?
- An electric field
- Magnetic field
How can you increase the spacing between the maxima in an intereference pattern produced by a monochromatic light source and a grating?
- Decrease the separation of the sources (slit separation)
- Increase the wavelength of the light source
- Increase the distance between the sources and screen/detector (grating to screen distance)
Give one advantage of producing electricity by nuclear fusion.
- Abundant fuel supply (Deuterium can be extracted from sea water)
- Safe (Small amounts of fuel, if reaction is unchecked it results in it stopping)
- Clean (No combustion so no air pollution)
- Less nuclear waste (waste is not high level weapons grade, needs stored for about 100 years)
- Efficient (1kg fusion fuel gives same energy as 10 million kg of fossil fuels)
What is meant by diffraction?
Diffraction is the bending of waves round an object.
Describe the electric field around a negative charge.
Field lines towards negatively charged particle.
What is meant by a Meson?
Mesons are made from 2 quarks.
They always consist of a quark and an antiquark pair.
Describe the electric field around a positive charge.
Field lines away from the positive charge.
What are the names of the 6 types of Leptons?
- Electron
- Electron neutrino
- Muon
- Muon neutrino
- Tau
- Tau Neutrino
What is the frequency of a wave?
The number of waves per second.
What represents a magnetic field coming ‘out of the page’?
A dot
A proton is made up of two up quarks and a down quark. The up quarks are both positively charged. Why does the proton not get torn apart?
Gluons carry the strong force to hold the quarks together. This strong force is greater than the force of repulsion between the particles.
If white light is shone through a grating what does the interference pattern look like?
- The central order maximum will be white
- At every other maxima a spectrum will be produced
What is the wavelength of a wave?
Wavelength is the distance from a point on one wave to the same point on the next wave.
How does an antimatter particle compare with a matter particle?
Antimatter particle has similar properties to the matter particle but equal and opposite charge.
Describe the field lines between two negative charges.
The field lines run towards the negative charges but no filed lines between them.
What is meant by a Hadron?
Particles made from quarks
In the photoelectric effect, if the frequency of the incident radiation is increased what happens?
The electrons ejected will have more kinetic energy, if the frequency is greater than the threshold frequency.
What can you say about electrons absorbing photons in the photoelectric effect?
- An electron can only absorb the energy from one photon
- The electron absorbs all the energy from the photon.
What is the ground state?
This is the energy level with the least energy. It is the most negative energy level.
What is the Law of Reflection?
Angle of incidence = Angle of reflection
Why were neutrinos suggested as an extra particle produced as a result of beta decay?
When beta decay occurs momentum and energy should be conserved. This was not happening if only the proton and beta particle were considered. There had to be another particle that carried the rest of the energy away.
What is the Standard Model?
The Standard Model explains how the basic building blocks of matter interact, governed by four fundamental forces.
What is constructive intereference?
This occurs when two waves meet at a point in phase.
What do absorption lines in the Sun’s spectrum show?
Evidence for the composition of the upper atmosphere of the Sun.
What is meant by irradiance?
The power per unit area
What are the main features of the Bohr model of the atom?
- Positively charged central nucleus.
- Electrons (negatively charged) are in discrete energy levels and do not radiate energy
- When an electron makes a transition from one energy level to another a specific amount of energy is lost or gained
- Each line in a spectrum is produced when an electron moves from one energy level to another.
What evidence is there for antimatter?
Positrons discovered ocurring naturally in cosmic rays.
What is a coherent source?
Waves that have a constant phase difference (and the same frequency, wavelength and velocity)
In a fusion reactor why are the high temperatures required a problem?
High temperature required to give the hydrogen atoms enough energy to overcome the electrical repulsion between the protons. This is difficult to contain as all materials would vaporise at this temperature.
Containment and cooling are issues associated with a nuclear fusion reactor. Why?
Temperature of the reaction is so high most materials will vaporise. So a magnetic field can be used to suspend the plasma away from the sides of the container.
This requires strong magnetic fields produced by superconducting coils. These only work at cery low temperatures so need good cooling systems.
Describe the field lines between two positive charges.
Field lines run away from the positive charges. No field lines between them.
What is a point source?
This is a source where the light spreads evely in all directions
In the photoelectric effect, what happens to the maximum kinetic energy of an electron if the irradiance is increased?
Why?
- There is no effect on the maximum kinetic energy it remains the same.
- The energy of the incident photons (E = hf) is unchanged.
What force is carried by a Gluon?
Strong force
Name the four Bosons.
- Photons
- W and Z Bosons
- Gluons
- Gravitons
What are the advantages of using a grating to produce an interference pattern instead of a double slit?
- Fringes are brighter
- Fringes are sharper
What is meant by a Baryon?
Baryons are made from 3 quarks
If an unstable nucleus undergoes beta decay what is given out and what is the effect on the mass number and the atomic number?
An electron from the nucleus is given out along with an antineutrino.
The mass number of the product remains the same and the atomic number increases by one.
What is the amplitude of a wave?
The distace from the centre of a wave to the crest or trough.
What did beta decay provide the first evidence for?
The existence of neutrinos.
What is the effect of an electric field on a charged particle?
The particle will experience a force that causes an acceleration.
Explain how a particle accelerator works.
- Acceleration of charged particles - use an electric field which causes particles to experience a force and accelerates them.
- Deflection of charged particles - magnetic fields are used to chage the direction of the moving charged particles.
- Collision of charged particles - against a fixed target or between two beams of particles.
Are all photons produced by energy level transitions visible?
No, some frequencies of photons may be in in the ultraviolet or X-ray frequency
What are the fingers representing in the right hand rule?
- First Finger - Field (Magnetic field)
- SeCond finger - Current
- THumb - Thrust (Movement)
What is the Work Function?
The minimum energy required to eject an electron from a metal surface.
What is a Boson?
Bosons are force carrying particles.
If an incident photon is greater than the work function what happens to the rest of the photon’s energy?
The electron that is ejected has the rest of the energy as kinetic energy.
Why does the photoelectric effect give evidence for light to be considered as a particle?
- Photoelectric effect cannot be explained if light is thought of as a wave or any light would cause photoemission if it shone on the surface long enough to deliver enough energy to the electrons..
- Each photon contains a discrete amount of energy which results in one photon ejecting one electron
What 2 conditions are required for nuclear fusion?
- High Temperatures
- High Pressure
What is refraction?
The change in speed of light (and wavelength) as it enters a different material, this can result in a change in direction.
What is the photoelectric effect?
The photoelectric effect is when electromagnetic radiation is directed at a metal surface and ejects electrons from the surface.
What type of spectrum is this?
Line emission spectrum
Using a grating how can you increase the spacing between the maxima?
- Use a grating with a smaller slit separation.
- Use a source with a greater wavelength of light
- Move the screen further away
What are the two types of Fermions?
Quark
and
Lepton
What is irradiance?
The power per unit area
What force is carried by a photon?
Electromagnetic Force
Describe the field lines between parallel plates.
Field lines run from positive to negative plates.
What is meant by fusion?
Fusion is when two small mass number nuclei combine to form a nucleus of a larger mass number.
Give an example of a Baryon.
Proton
Neutron
What force is carried by W and Z bosons?
Weak force
What is the threshold frequency?
The minimum frequency of light required to eject an electron from a metal surface.
In the equation E = mc2 , what does the m stand for?
The mass which is converted into energy, which is the difference in mass of the particles before the fission/fusion reaction and the mass after.
What is a maxima?
A point where constructive interference occurs.
In the photoelectric effect, if the irradiance of the incident radiation is increased what will happen?
- No electrons will be ejected if the frequency of the incident radiation is below the threshold frequency.
- If the frequency is above the threshold frequency then more electrons will be ejected from the surface.
What force is carried by a Graviton?
Gravity force
What is meant by absolute refractive index?
It is the ratio of speed of light in a vacuum to the speed of light in the material.
How are absorption lines in the Sun produced?
Photons of certain frequencies are absorbed by the gases in the outer atmosphere of the Sun.
What is a minima?
A point where destructive interference occurs.
What are the 4 differences in spectra produced by refraction (in a prism) and by a grating?
Prism Grating
One spectrum Many spectra
Produced by Refraction Produced by interference
Red light deviated least Red light deviated most
Spectrum is dim Spectrum is bright
What is a Fermion?
It is a matter particle.
What is destructive interference?
Destructive interference occurs when two waves meet at a point exactly 180O out of phase.
Does a particle accelerator use a.c. or d.c. to create the electric field?
Explain why.
a.c.
This is because the electric field must change direction every time a particle completes a half circle (Dee) to keep the accelerating potential in the correct direction for the particles motion.
If an unstable nucleus undergoes alpha decay what is given out and what is the effect on the mass number and the atomic number?
An alpha particle is a helium nucleus.
Mass Number - This means that the product mass number + the mass number of a helium nucleus = mass number of the original unstable nucleus.
Atomic Number - This means that the product atomic number + the atomic number of a helium nucleus = atomic number of the original unstable nucleus.
What is the definition for a potential difference of 1 Volt?
There is a potential difference of 1 Volt between two points if I joule of energy is required to move 1 coulomb of charge between the two points.
