Particles and Radiation

Charge on a proton/electron

1.6 × 10^-19 C

Specific charge

Charge-to-mass ratio (Q/m)

Carbon dating

Finding the percentage of carbon which is C-14 in a sample and using the known starting value to estimate an age

SNF

Strong Nuclear Force

What does the SNF do and what does it act on?

Keeps nuclei stable. It only acts on nucleons.

Ranges of the SNF

<0.5 fm → Repulsive

0.5-3.0 → Attractive

>3.0 → Negligible

Alpha decay

An unstable nuclei will emit an alpha particle/helium nucleus, which is 2 protons and 2 neutrons.

Beta-minus decay

An unstable nuclei will emit a beta particle/electron and an anti-electron neutrino

Beta-plus decay

An unstable nuclei will emit a positron/anti-beta particle and an electron neutrino

Gamma decay

A nucleus will emit a high energy photon from an electron changing shell

Photon energy

E = hf = hc/λ

Annihilation

When a particle and its anti-particle collide and their (rest) masses are converted into energy. This energy is then released in the form of two photons

Pair production

When a photon spontaneously converts into matter and anti-matter particles (such as an electron-positron pair).

Fundamental forces

Gravity

Electromagnetic

WNF

SNF

Exchange particles

Exchange particles are particles which carry energy and momentum between the particles experiencing a force

SNF

Exchange particle → Gluon

Range → 3 × 10^-15 m

Acts on → Hadrons

WNF

Exchange particle → W boson

Range → 10^-18 m

Acts on → All particles

Electromagnetic

Exchange particle → Virtual photon

Range → Infinite

Acts on → Charged particles

Gravitational

Exchange particle → Graviton (Theorised)

Range → Infinite

Acts on → Particles with mass

Electron capture

p + e^- → n + v_e

Two major particle classifications

Hadrons & Leptons

Subgroups of hadrons

Baryons and mesons

Baryons

3 quarksM

Mesons

2 quarks

What is the only stable baryon?

Proton

For which type of interaction must strangeness be conserved?

Strong

How are strange particles produced?

Strong nuclear interactions

How do strange particles decay?

Weak nuclear interactions

Strangeness of a strange quark

-1

When must strangeness be conserved?

Strong interactions

Photoelectric effect

When (photo)electrons are emitted from the surface of a metal after light above a certain frequency is shone incident on it.

What is threshold frequency?

The frequency above which photoelectrons are emitted from the surface of a metal.

Why can the photoelectric effect be explained by the particle model of light?

EM radiation travels in discrete packets (photons), which have a direct relationship between energy and frequency.

Each electron in a metal can absorb a singular photon

If the light intensity increases, only the rate of emission of photoelectrons is affected (if frequency >= threshold frequency)

Work function

Minimum required energy for electrons to be emitted from the surface of a metal

Stopping potential

The theoretical potential difference required to stop photoelectrons with the maximum possible kinetic energy.

Stopping potential equation

E_{k (max)} = eV_s

Photoelectric equation

E (= hf) = ϕ + E_{k (max)}

What is electron excitation?

When orbital electrons gain energy via collisions and move up an energy level.

What is electron ionisation?

When orbital electrons gain energy via collisions and move out of the energy shells of an atom.

What is electron deexcitation?

When an excited electron becomes unstable and moves back to its original energy level, emitting a photon with energy equivalent to the difference in energy levels.

Fluorescent mercury tube

A tube filled with mercury vapour, across which a high voltage is applied, causing electrons to excite and excite electrons from the fluorescent paint on the side of the tube (which deexcite and produce visible light).

An electron volt (eV)

Energy gained by one electron when passing through a potential difference of 1 volt

Conversion factor from eV and J

1.6 × 10^-19 (eV > J)

Electron diffraction

When electrons are passed through a slit and form an interference pattern of concentric rings made up of lines and dots.

De Broglie wavelength

The wavelength of a particle or solid objectD

De Broglie wavelength equation

λ = h/mv