Unit 2 - Particles and Waves Flashcards
(38 cards)
What are fundamental particles?
Fundamental particles are not composed of other particles. This means that fundamental particles cannot be ‘broken down’ into smaller particles.
What are fermions?
Matter particles (if a particle has mass then it must be a fermion). Quarks and Leptons.
What types of leptons are there?
Electrons, muons, tau and 3 neutrinos.
What are bosons?
Force mediating particles.
Gluon - strong force
W and Z bosons - weak nuclear force
Graviton - Gravitational force
Photon - Electromagnetic force
What are hadrons?
mesons and baryon.
What are mesons made of?
One quark and one antiquark.
What are baryons made of?
3 quarks OR 3 antiquarks.
What is proof of the antineutrino and therefore the neutrino?
Beta decay.
What is potential difference of two points in an electric field?
A measure of the work done (W) in moving a coulomb of charge (Q) between the two points.
Explain how a cyclotron accelerator works
Ions are injected at a point near the centre. An alternating potential difference between the ‘dee’ shaped electrodes accelerates the particles. A magnetic field causes the particles to move in a circular path. When the particle crosses from one ‘dee’ to another it accelerates. After each acceleration, the particle moves to a slightly larger orbit. When it reaches the outer edge of the cyclotron the particle beam is extracted and used in other experiments.
Explain how a linear accelerator (LINAC) works.
Charged particles are accelerated in a vacuum pipe through a series of electrodes by an alternating voltage. The beam of particles is then directed at a target or into a synchrotron.
Explain how a synchrotron works.
This is similar to a linear accelerator, bent into a ring so the charged particles can be given more energy each time they go round. Electromagnets keep the particles in a curved path. As the speed increases, the magnetic field strength is increased. As the speed increases and relativistic effect cause the mass of the particles to increase, a larger force is needed to accelerate them and keep them in a circular path.
What is meant by the term nuclear fusion?
Two small nuclei combine to form a larger nucleus.
Why is energy released in nuclear reactions?
Some mass is lost and converted to energy.
Why do you need magnetic fields to contain plasma inside a fusion reactor?
Plasma would cool down if it came too close to the sides OR plasma would melt the sides of the reactor.
What is threshold frequency (f₀)?
Threshold frequency is the minimum frequency of a photon required to cause photoemission (an electron to be ejected)
What is work functions (hf₀)?
Work function is the minimum energy required to cause photoemission (an electron to be ejected)
What is constructive interference?
When waves meet in phase
What is destructive interference?
When waves meet exactly (180°) out of phase
What is absolute refractive index (n)?
Absolute refractive index of a medium is the ratio of the speed of light in a vacuum to the speed of light in
a medium.
What is the critical angle?
Critical angle is the angle of incidence that causes the angle of refraction to be 90°
What is irradiance (I)?
Irradiance is the power per unit area (incident on a surface).
Describe what 6Wm^-2 means.
If there is an irradiance of 6 W m-2 at a surface, this means that 6 W of power is incident on 1 square metre
of surface.
Explain why the photoelectric effect provides evidence for the particle nature of light
Each photon contains a fixed amount of energy. If light was a wave then the photoelectric effect would occur regardless of the frequency of the light, it would just take longer for electrons to absorb the energy required to be ejected.
