Physics: Particle Physics

What is found at the centre of an atom?

A small nucleus.

What particles are found in the nucleus?

Protons and neutrons.

What particles orbit the nucleus?

Electrons.

What is the charge of a proton?

+1.6 × 10⁻¹⁹ C

What is the charge of a neutron?

0 C

What is the charge of an electron?

−1.6 × 10⁻¹⁹ C

What is the mass of a proton?

1.67 × 10⁻²⁷ kg

What is the mass of a neutron?

1.67 × 10⁻²⁷ kg

What is the mass of an electron?

9.11 × 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 relative mass of a proton?

1

What is the relative mass of a neutron?

1

What is the relative mass of an electron?

0.0005

What does the proton number represent?

The number of protons in the nucleus.

What symbol is used for proton number?

Z

What does the nucleon number represent?

The total number of protons and neutrons.

What symbol is used for nucleon number?

A

What is the proton number of helium?

2

What is the nucleon number of helium-4?

4

What determines the identity of an element?

The proton number.

What is hydrogen-1 made of?

One proton.

What is deuterium?

Hydrogen-2 with one proton and one neutron.

What is tritium?

Hydrogen-3 with one proton and two neutrons.

Define an isotope.

Atoms with the same number of protons but different numbers of neutrons.

Give one use of isotopes.

Carbon dating.

Give another use of isotopes.

Medicine.

Which isotope is used in carbon dating?

Carbon-14.

What ratio is constant in living organisms?

Carbon-14 to carbon-12.

Why is carbon-14 radioactive?

It is an unstable isotope.

How is carbon-14 produced?

By cosmic rays interacting with the atmosphere.

What happens to the carbon-14/carbon-12 ratio after death?

It decreases.

How is isotopic data used in carbon dating?

To calculate the age of objects.

Define specific charge.

Charge divided by mass.

State the equation for specific charge.

Q/m

What are the units of specific charge?

C kg⁻¹

Calculate the specific charge of a proton.

9.6 × 10⁷ C kg⁻¹

What force attracts particles in the nucleus due to mass?

Gravity.

Is gravity significant inside the nucleus?

No, it is very weak.

What force causes repulsion between protons?

Electrostatic repulsion.

Why do protons repel each other?

They have the same positive charge.

What force holds the nucleus together?

The strong nuclear force.

Why doesn't the nucleus fly apart?

The strong nuclear force overcomes electrostatic repulsion.

What happens when a nucleus becomes too large?

It may become unstable and decay.

What is alpha decay?

Emission of an alpha particle from a nucleus.

What is an alpha particle?

A helium nucleus ⁴₂He

Write the alpha decay equation for uranium-238.

²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He

What happens to the nucleon number during alpha decay?

It decreases by 4.

What happens to the proton number during alpha decay?

It decreases by 2.

What is beta minus decay?

A neutron changes into a proton and emits an electron and antineutrino.

Write the beta minus decay equation for carbon-14.

¹⁴₆C → ¹⁴₇N + e⁻ + ν̄ₑ

What particle is emitted in beta minus decay?

An electron.

What is another name for a beta particle?

An electron.

What additional particle is emitted in beta minus decay?

An electron antineutrino.

Which force is responsible for beta decay?

The weak nuclear force.

What happens to the proton number during beta minus decay?

It increases by 1.

What happens to the nucleon number during beta minus decay?

It remains unchanged.

What happens to a neutron during beta minus decay?

It turns into a proton.

What is an antiparticle?

A particle with the same mass but opposite charge.

What is the antiparticle of the electron?

The positron.

What is the antiparticle of the proton?

The antiproton.

What is the antiparticle of the neutron?

The antineutron.

What is the mass of a positron?

9.11 × 10⁻³¹ kg

What is the charge of a positron?

+1.6 × 10⁻¹⁹ C

What is the charge of an antiproton?

−1.6 × 10⁻¹⁹ C

What property is the same for a particle and its antiparticle?

Mass.

What property is opposite for a particle and its antiparticle?

Charge.

What is the charge of an antineutron?

0

What is the symbol for an electron neutrino?

νₑ

What is the symbol for an electron antineutrino?

ν̄ₑ

What is the charge of a neutrino?

0

What is the mass of a neutrino?

Negligible.

What is rest energy usually measured in?

MeV

What is the rest energy of an electron?

0.511 MeV

What is the rest energy of a positron?

0.511 MeV

What is the rest energy of a proton?

938 MeV

What is the rest energy of a neutron?

939 MeV

What is electromagnetic radiation made of?

Photons.

What is a photon?

A particle of electromagnetic radiation.

State the photon energy equation.

E = hf

What is Planck's constant?

6.63 × 10⁻³⁴ J s

State the wave equation.

c = fλ

State the alternative photon energy equation.

E = hc/λ

What is annihilation?

When a particle and antiparticle meet and convert all their mass into energy.

What happens when an electron and positron annihilate?

Two photons are produced.

What is conserved during annihilation?

Energy.

What is the maximum wavelength of photons produced in electron-positron annihilation?

2.43 × 10⁻¹² m

What is pair production?

A photon creating a particle-antiparticle pair.

What is the minimum condition for pair production?

Photon energy must be at least twice the rest energy of the particles.

State the pair production condition.

E_min = 2E₀

What is a fundamental force?

A force that cannot be explained in terms of another force.

How many fundamental forces are there?

Four.

Name the four fundamental forces.

Electromagnetic, weak nuclear, strong nuclear and gravitational.

Which fundamental force is responsible for nuclear decay?

Weak nuclear force.

Which force holds nuclei together?

Strong nuclear force.

Which force acts between charged particles?

Electromagnetic force.

Which force is weakest?

Gravity.

What carries the electromagnetic interaction?

Virtual photons.

What is an exchange particle?

A particle that carries a force.