Chapter 15: Radiation

Question 1

What is background radiation defined as?

Answer 1

The radiation that exists around us all the time

Question 2

What are the two main sources of background radiation?

Answer 2

Natural: Radon Gas, Rocks, Cosmic Rays, Carbon-14 in Biological Material
Man-made: Medical Sources, Nuclear Waste, Nuclear Fallout and Accidents

Question 3

What is the name given to the amount of radiation a person recieves?

Answer 3

A dose

Question 4

How is ionising nuclear radiation measured?

Answer 4

Using a detector that is connected to a counter

Question 5

What is a count rate?

Answer 5

The number of decays per second detected by a detector and recorded by the counter
Measured in counts/min or counts/s

Question 6

How is the count rate related to the distance the detector is from the source?

Answer 6

Inversely related, as the radiation spreads out more the further away the counter is from the source

Question 7

What is the most common device used to measure and detect radiation?

Answer 7

Geiger-Muller tube

Question 8

What is the unit of activity?

Answer 8

Becquerel (Bq) or Disintergrations per second
SI Units: Becquerel (Bq)

Question 9

What is the mass number of an atom?

Answer 9

The number of protons and neutrons in a nucleus of an atom

Question 10

What is the atomic (proton) number of an atom?

Answer 10

The number of protons in a nucleus of an atom

Question 11

What are Isotopes?

Answer 11

The same element with a different number of neutrons / different mass

Question 12

What is radioactive decay?

Answer 12

When an unstable nucleus stablises itself by decaying, emitting alpha particles, beta particles, gamma rays or neutrons

Question 13

When does a nucleus undergo alpha decay?

Answer 13

When the nucleus has too few neutrons

Question 14

What does alpha decay emit?

Answer 14

A particle containing 2 neutrons and 2 protons, or a Helium-4 nucleus (alpha particle)

Question 15

How does alpha decay affect the mass and atomic number of the nucleus?

Answer 15

Alpha decay causes mass number to decrease by 4, and atomic number to decrease by 2

Question 16

When does a nucleus undergo beta decay?

Answer 16

When the nucleus has too many neutrons

Question 17

What happens during beta decay?

Answer 17

A neutron will decay into a proton, a fast moving electron (and an anti-neutrino). The electron (or beta minus particle) is emitted

Question 18

How does beta decay affect the mass and atomic number of the nucleus?

Answer 18

Beta decay causes atomic number to increase by 1, and mass number remains unchanged

Question 19

Why does gamma radiation occur?

Answer 19

Even after undergoing alpha or beta decay, the nucleus will often still be too hot, and will have to emit an electromagnetic wave, called a gamma ray

Question 20

What is neutron emission?

Answer 20

When a nucleus has too many neutrons or too few protons, the nucleus will emit one or more neutrons

Question 21

How does neutron emission affect mass and atomic number of the nucleus?

Answer 21

Neutron emission causes mass number to decrease by one, and atomic number remains unchanged

Question 22

What is alpha and beta particles, and gamma rays penetrating power?

Answer 22

Alpha particle: Skin / Paper
Beta particle: 3 mm aluminium foil
Gamma ray: Lead / Concrete

Question 23

What is alpha and beta particles, and gamma rays ionising power?

Answer 23

Alpha particle: High
Beta particle: Low
Gamma ray: Very low

Question 24

What is alpha and beta particles, and gamma rays range in air?

Answer 24

Alpha particle: Less than or equal to 5 cm
Beta particle: Around 1 m
Gamma ray: More than 1 km

Question 25

What is the half-life of an atom / nucleus?

Answer 25

The time it takes for half of the unstable nuclei in a sample of nuclei to decay or for the count rate / activity to half

Question 26

What is the difference between nucleur fusion and fission

Answer 26

Nucleur fission is when a nucleus splits into two smaller nucleus, nucleur fusion is when two smaller nucleus join to form a bigger nucleus

Question 27

What equation connectes the small amount of the particle’s mass being converted to energy?

Answer 27

Energy (E) = Mass (m) x Speed of light^2 (c^2)

Question 28

How does radiation negatively impact the human body?

Answer 28

The genetic material of the cell (DNA) can be damaged via ionisation, which can lead to cancer. Radiation can also deposit large amounts of energy into the body, which can damage and destroy cells

Question 29

When can alpha, beta and gamma radiation harm the body?

Answer 29

Alpha radiation: When source is inside the body
Beta and Gamme radiation: When source is both inside and outside the body

Question 30

What are some negative impacts of radiation on the eyes, thyroid, lungs, stomach, reproductive organs, skin and bone marrow?

Answer 30

Eyes: Cataracts
Thyroid: Thyroid cancer
Lungs: Damage DNA through breathing of radioactive isotopes
Stomach: Radioactive material can sit in stomach andd irradiate for a long time
Reproductive organs: Sterility or mutation
Skin: Burns or skin cancer
Bone marrow: Leukaemia and other blood diseases

Question 31

How does gamma rays help detect tumours?

Answer 31

Tcchnitium 99 can be taken into the body which allows a gamma camera to show images of internal organs via gamma rays

Question 32

How does beta particles help treat thryoid disorder?

Answer 32

Beta particles in Iodine 131 will destroy thyroid cells, including cancerous cells. As the isotope only has a half life of 8 days, it will not remain in the body for very long