1. Particle Physics Flashcards
What makes up an atom?
a nucleus and electrons
What makes up the nucleus?
protons and neutrons
What are protons and neutrons?
nucleons
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
1/2000
What is the mass of a proton?
1.67 x 10^-27 kg
What is the mass of a neutron?
1.67 x 10^-27 kg
What is the mass of an electron?
9.11 x 10^-31 kg
What is the relative charge of a proton?
+1
What is the relative charge of a neutron?
0
What is the relative charge of an electron?
-1
What is the charge of a proton?
+1.60 x 10^-19 C
What is the charge of a neutron?
0 C
What is the charge of an electron?
-1.60 x 10^-19 C
What is nuclide notation?
how information on elements is displayed on the periodic table
What is an isotope?
at atom with the same number of protons but a different number of neutrons
What happens when you change the number of protons in an atom?
create a new element
What happens when you change the number of neutrons in an atom?
create an isotope
What happens when you change the number of electrons in an atom?
create a new ion
What does isotopic data mean?
the relative amounts of the different isotopes of an element present in a substance
What happens to unstable nuclei over time?
they decay into more stable nuclei over time
How can you estimate a material’s age?
by looking at the amount of isotopes in the material
What is specific charge?
the amount of charge an object has per kilogram
What three things could you be asked to find the specific charge of?
- a single particle
- a nucleus
- an ion
How do you calculate the specific charge?
total charge/total mass
What is specific charge measured in?
Ckg^-1
What is meant by the relative mass of an atomic constituent?
relative mass is the mass relative to a proton’s mass, as opposed to the actual mass
In nuclide notation, what does ‘A’ represent?
nucleon number
In nuclide notation, what does ‘Z’ represent?
proton number
In nuclide notation, what does ‘X’ represent?
element symbol
What does isotopic data mean?
the relative amounts of the different isotopes of an element present in a substance
What are the four fundamental forces?
- gravity
- electromagnetic
- strong nuclear
- weak nuclear
Outline gravity
all objects with mass are attracted to each other
Outline the electromagnetic force
all objects with charge are either attracted to or repelled from each other
Outline the strong nuclear force
responsible for holding the nucleus of atoms together and responsible for the decay and creation of particles
Outline the weak nuclear force
responsible for the decay and creation of particles
What is the name of the force that holds nucleons together inside the nucleus?
strong nuclear force
Why must the strong nuclear force exist?
the repulsion of protons due to the electromagnetic force is much greater than the gravitational attraction, so there must be another attractive force to hold the nucleus together
Which particles does the strong nuclear force affect?
both nucleons (protons and neutrons)
What type of force is the SNF?
can either be attractive or repulsive
What does the type of SNF depend on?
distance between particles
What range does the SNF have?
very short range
When is the SNF repulsive?
if nucleons are 0-0.5fm apart
When is the SNF attractive?
if nucleons are 0.5-3fm apart
When does the SNF have no effect?
if nucleons are beyond 3fm apart
Why do nuclei emit alpha and beta particles?
because they are unstable
What are the three main reasons for a nucleus being unstable?
- too much mass
- imbalance of protons and neutrons
- too much energy
How can a nucleus with too much mass become more stable? What is this called?
eject some particles (alpha decay)
How can a nucleus with an imbalance of nucleons become more stable? What is this called?
weak nuclear force can change the particle type (beta +/- decay)
How can a nucleus with too much energy become more stable? What is this called?
release some energy (gamma decay)
What is an alpha particle?
2 protons and 2 neutrons (helium nucleus)
When is an alpha particle emitted?
when a particle undergoes alpha decay
In what type of nucleus does alpha decay usually occur?
very heavy nuclei
What is the proton number of an alpha particle?
2
What is the nucleon number of an alpha particle?
4
In what type of nucleus does beta-minus decay usually occur?
neutron-rich
What happens during beta-minus decay?
a neutron turns into a proton via the weak nuclear force, emitting a beta-minus particle and an anti-neutrino
Which particle is a beta-minus particle identical to?
electron
Name three pieces of equipment which could be used to detect alpha and beta radiation
- geiger counter
- spark counter
- cloud chamber
How did observations of beta-minus decay lead to the prediction of the neutrino?
- the total energy of the particles emitted in beta-minus decay was less than the energy before
- this energy couldn’t be accounted for by the recoil of the nucleus
- therefore there must be another particle carrying away the missing energy
What are photons?
described as ‘packets’ of electromagnetic waves
What are the similarities and differences between photons?
they can have different frequencies, wavelengths and energies, but they all travel at the speed of light
What is the speed of light?
3.00 x 10^8 m/s
How is the energy of a photon related to its frequency?
directly proportional
What is the value of Planck’s constant?
6.63 x 10^-34 (m^2kg/s)
State the equation linking energy of photons (E), Planck’s constant (h) and frequency (f)?
E = hf
State the equation linking the energy of photons (E), Planck’s constant (h), speed of light (c) and wavelength (λ)?
E = (hc)/λ
What is annihilation?
when a particle and its corresponding antiparticle meet and their mass (and kinetic energy) is converted into two photons, travelling in opposite directions to conserve momentum
What is pair production?
when a photon with enough energy converts its energy into a particle and its corresponding antiparticle pair