Particles and radiation chapter 1: Matter and radiation

Question 1

Describe the structure of an atom.

Answer 1

Atoms are mode up of a nucleus and atomic orbitals (electron shells).

The nucleus solely contains protons and neutrons, being situated in the centre of an atom being very small.

The orbitals contain electrons of specific shells which orbit the nucleus.

Question 2

Define the term isotope.

Answer 2

isotopes are atoms with the same number of protons but a different number of neutrons.

Question 3

What is meant by the term specific charge?

Answer 3

The specific charge is the charge/mass ratio of a charged particle, and is measured in Coulombs per kilogram (Ckg^-1).

Question 4

What do the letters A, Z and X denote?

Answer 4

A is the nucleon number (no. of protons and neutrons in the atom)

Z is the proton number (no. of protons in the atom)

X stands for the symbol of the element.

Question 5

Carbon-14 is a radioactive isotope of carbon. State a use for this isotope.

Answer 5

Carbon-14 can be used to find the approximate age of an object containing organic material. This is done through carbon dating which involves calculating the percentage of carbon 14 remaining in an object and using the known starting value of carbon-14 (which is the same for all living things), and it’s half-life to calculate an approximate age.

Question 6

How does the strong nuclear force (SNF) work?

Answer 6

The strong nuclear force keeps nuclei stable by counteracting the electrostatic force of repulsion between equally charged protons in the nucleus.

Question 7

What is the strong nuclear force (SNF)?

Answer 7

The strong nuclear force attractive force between nucleons (neutron or proton in the nucleus) that holds the nucleons in the nucleus.

Question 8

State the range of the strong nuclear force, and draw a graph to demonstrate the concept.

Answer 8

The strong nuclear force is attractive up to separations of 3 fm, but repulsive below separations of 0.5 fm.

Question 9

what makes a nucleus unstable?

Answer 9

A nucleus is unstable when it has too many protons or neutrons, causing the strong nuclear force to become much less effective.

Nucleons in a nucleus will decay in order to regain stability. The type of decay is dependent on the number of each nucleon in the nucleus.

Question 10

State what is meant by alpha decay and write a general equation.

Answer 10

Alpha decay occurs in large nuclei with too many of both protons and neutrons.

• Proton number decreases by 2
• Nucleon number decreases by 4
• An alpha particle is emitted

Question 11

State what is meant by beta minus decay and write a general equation.

Answer 11

Beta minus decay occurs in nuclei which are neutron-rich (too many neutrons).

A neutron changes into a proton.

• The proton number increases by 1
• The nucleon number stays the same
• A beta particle (electron) and an electron antineutrino are emitted

Question 12

Define the term “antiparticle”

Answer 12

Each particle has an antiparticle which has the same rest energy and mass but all its other properties are opposite.

Question 13

Define the term “photon”

Answer 13

A photon is a packet of electromagnetic waves which transfer energy and have no mass.

Question 14

Explain the process of annihilation

Answer 14

Annihilation is where a particle and its corresponding antiparticle collide, as a result the two masses are converted into energy. This energy, along with the kinetic energy of the two particles is released in the form of 2 photons moving in opposite directions in order to conserve momentum.

Question 15

Draw a diagram showing the process of annihilation

Answer 15

Question 16

Give an example of an application of annihilation

Answer 16

One application is in a PET scanner.

• Allows 3-D images of the inside of the body to be taken, which makes medical diagnosis easier.
• This is done by introducing a positron emitting radioscope into the patient.
• As positrons are released, they annihilate with electrons already in the patient’s system, emitting gamma photons which can easily be detected.

Question 17

Explain the process of pair production

Answer 17

Pair production is where a photon is converted into a particle and antiparticle-this can only occur when the photon has an energy greater than than the total rest energy of the two particles. Any excess energy is converted into kinetic energy.

Question 18

Draw a diagram demonstrating pair production

Answer 18

Question 19

What are the four fundamental forces?

Answer 19

• Gravitational force
• Electromagnetic force
• Weak nuclear force
• Strong nuclear force

Question 20

Define the term “exchange particle”

Answer 20

• Exchange particles carry energy and momentum between the particles experiencing the force
• Each fundamental force has its own exchange particle.

Question 21

For the strong interaction, state the exchange particle, its range (m) and which group of particles it acts on.

Answer 21

• Exchange particle: Gluon
• Range (m): 3×10^-5
• Acts on: Hadrons

Question 22

For the weak interaction, state the exchange particle, its range (m) and which group of particles it acts on.

Answer 22

• Exchange particle: W boson (W+ or W-)
• Range: 10^-18
• Acts on: all particles

Question 23

For the electromagnetic interaction, state the exchange particle, its range (m) and which group of particles it acts on.

Answer 23

• Exchange particle: virtual photon (γ)
• Range (m): infinite
• Acts on: Charged particles

Question 24

For the gravitational interaction, state its range (m) and which group of particles it acts on.

Answer 24

• Range (m): infinite
• Acts on: Particles with mass

Question 25

What is the WNF responsible for?

Answer 25

• Beta decay (+ or -)
• electron capture
• electron-proton collisions

Question 26

Draw a diagram representing electron capture and write an equation.

Answer 26

Question 27

draw a diagram representing electron-proton collision and write an equation.

Answer 27

Question 28

Draw a diagram representing beta plus decay and write an equation.

Answer 28

Question 29

Draw a diagram representing beta minus decay and write an equation.

Answer 29

Question 30

Define the term “nucleon”

Answer 30

A neutron or proton in the nucleus.

Question 31

Define the term “nuclide”

Answer 31

A type of nucleus with a particular number of protons and neutrons.

Question 32

1 fm = ? m

Answer 32

10^-15 m

Question 33

What is an alpha particle comprised of?

Answer 33

Two protons and two neutrons.

Question 34

What is gamma radiation?

Answer 34

• gamma radiation is electromagnetic radiation emitted by an unstable nucleus with too much energy after alpha or beta emission.
• it has no mass or charge.
• It can pass through thick metal plates.

Question 35

What is the photoelectric effect?

Answer 35

The emission of electrons from a metal surface when electromagnetic radiation is incident upon it.

Question 36

When can a charged particle emit photons?

Answer 36

• When an electron is stopped, slows down or changes direction.
• when an electron moves to a shell of lower energy in an atom.

Question 37

What’s the equation for photon energy?

Answer 37

E = hf

Question 38

What value is the Planck constant?

Answer 38

6.63*10^-34 J

Question 39

What is antimatter?

Answer 39

Antiparticles that each have the same rest mass and, if charged, have equal and opposite charge to the corresponding particle.

Question 40

What’s a positron?

Answer 40

The antiparticle of the electron.

Question 41

Define rest energy.

Answer 41

Energy due to mass m₀, equal to m₀c², where c is the speed of light in free space.