Nuclear

Question 1

Draw the binding energy per nucleon curve

Answer 1

Question 2

Atomic Spectra Model Answer

Answer 2

Explanation of line spectra:

Specific frequencies or wavelengths

Detail, e.g. absorption/emission

within narrow band of wavelengths

Explanation how line spectra provide evidence for existence or energy levels in atoms:

Photons

Associated with particular energies

Electron transitions

Discrete levels (to provide line spectra)

Question 3

Define Random and Spontaneous

Answer 3

Random means we cannot identify which atom/nucleus will be the next to decay

Or we cannot identify when an individual atom/nucleus will decay

Or we cannot state exactly how many atoms/nuclei will decay in a set time

Or we can only estimate the fraction that will decay in the next time interval

Spontaneous means that the decay cannot be influenced by any (external) factors.

Question 4

List sources of background radiation

Answer 4

Cosmic rays, rocks, soil, food, nuclear power/industry[buried waste as alternative], atmosphere, building material, medical uses, nuclear weapons testing (in the 60 s), Sun, radon gas

Question 5

Define Background Radiation and how to account for it

Answer 5

Radiation that comes from environmental sources including the earth’s crust, the atmosphere, cosmic rays, and radioisotopes

Subtract background (count rate) from readings

Question 6

Compare Alpha, Beta and Gamma Radiation

Answer 6

Composition

Alpha - Helium Nucleus, Beta - electrons, Gamma - electromagnetic radiation

Ionising Ability

Alpha - most, Gamma - least

Range

Alpha - short range in air (3 - 5 cm), stopped by paper

Beta - medium range in air (~15 cm), stopped by lead or thick aluminium

Gamma long range – inverse square law, attenuated by thick lead

Question 7

Give the equation for half life

Answer 7

A = A₀e^-λ​t

Question 8

Polarisation Model Answer

Answer 8

Transverse waves oscillate in any direction perpendicular to wave direction

Longitudinal waves oscillate in one direction only OR parallel to wave direction.

Polarisation reduces wave intensity by limiting oscillations and wave direction to only one plane OR limiting oscillations to one direction only.

Question 9

Define binding energy

Answer 9

Energy required to separate a nucleus (1) into nucleons (1)

Question 10

Outline the process of the fission and fusion

Answer 10

Fission

A heavy nucleus absorbs a neutron. [accepts “collides with” / “fired into” for “absorbs”]

The nucleus becomes unstable and splits into two (roughly equal sized) fragments [accept “decays” / “breaks up” for “splits”]

Idea that a few neutrons are also emitted in the fission process

These neutrons cause further fissions Or these neutrons cause a chain reaction

Fusion

(Small mass) nuclei come very close together Or strong (nuclear) force acts on nuclei

Nuclei join to form a more massive nucleus

Question 11

State the conditions needed for fusion

Answer 11

A very/extremely high temperature (plasma) is required

Plasma must not touch reactor walls, so strong magnetic fields are required Or If plasma touches the walls of the reactor its temperature falls (and fusion stops)

Very high temperatures [accept T~107 K] so that nuclei have sufficient energy to come close enough to overcome electrostatic repulsion [accept reference to strong interaction]

A collision rate large enough to sustain fusion (from a very high density)