Chapter 25 - Radiation

Question 1

Ionising Radiation

Answer 1

Radiation with enough energy to remove electrons from an atom

Question 2

Alpha radiation

Answer 2

2 protons, 2 neutrons

Q: +2e

Question 3

Beta plus radiation

Answer 3

Fast moving positron

Q: +e

Question 4

Beta minus radiation

Answer 4

Fast moving electron

Q: -e

Question 5

Gamma radiation

Answer 5

High energy photons (λ < 10^-13m)

Q: 0

Question 6

Radiation in EM fields

Answer 6

Gamma passes straight through
Beta minus attracted to the positive electrode/pole
Beta plus and alpha attracted to the negative electrode/pole, alpha has a weaker attraction

Question 7

Parent nucleus

Answer 7

The nucleus before a radioactive decay

Question 8

Daughter nucleus

Answer 8

The nucleus after the radioactive decay

Question 9

Transmutation

Answer 9

The process of a nucleus changing from one element to another

Question 10

Conservation in nuclear decay

Answer 10

Nucleon number, atomic number, charge, baryon and lepton numbers

Question 11

Alpha nuclear equations

Answer 11

A A-4 4
X —> Y + He/α
Z Z-2 2

Question 12

Beta minus nuclear equations

Answer 12

A A 0
X —> Y + e/β-
Z Z+1 -1

Question 13

Beta plus nuclear equations

Answer 13

A A 0
X —> Y + e/β+
Z Z-1 +1

Question 14

Gamma nuclear equations

Answer 14

A A
X —> X + γ
Z Z

Question 15

What is gamma decay

Answer 15

Emitted photons if there is excess energy after alpha, beta decay

Question 16

Decay chain

Answer 16

2D grid with Z along the top and A down the left. Draw a line and label with the type between each isotope it decays to

Question 17

Random decay

Answer 17

We cannot predict when a particular nucleus will decay or which nucleus in a sample will decay next. Each nucleus has an equal chance of decaying per unit time

Question 18

Spontaneous

Answer 18

The decay of the nuclei is not affected by the presence of other nuclei in the sample or other factors such as pressure

Question 19

Half-life definition

Answer 19

The average time it takes for half the number of active nuclei in a sample to decay
t
1/2

Question 20

Activity

Answer 20

The rate at which nuclei decay or disintegrate (decays per second/Bq)
Depends on the number of undecayed nuclei and the half-life of the source

Question 21

Decay constant formula

Answer 21

A = λN
Activity = decay constant x number of undecayed nuclei
For a sample with a very high number of undecayed nuclei

Question 22

Decay constant definition

Answer 22

The probability of decay of an individual nuclei per unit time
Units s^-1 or hrs^-1 or yrs^-1 but not Bq

Question 23

Radioactive decay exponential equations

Answer 23

N = N0 e^-λt

A = A0 e^-λt

Question 24

Half-life, decay constant relationship

Answer 24

λt = ln(2)

1/2

Question 25

Carbon dating

Answer 25

All life on Earth contains carbon
Atmospheric carbon is mostly stable Carbon-12 with some Carbon-14
The ratio of C-14 to C-12 is almost constant at 1.3x10^-12
When an organism dies it stops absorbing carbon and C-14 decays over time

Question 26

Carbon-14 half life

Answer 26

5700 years

Question 27

Carbon-14 formation

Answer 27

A cosmic ray hits N-14, causing a neutron to be absorbed and a proton emitted, leaving C-14

Question 28

Carbon-14 decay

Answer 28

β- to N-14

Question 29

Limitations of carbon dating

Answer 29

It is assumed that the ratio of C-14 to C-12 is constant
Increased emissions may have reduced the ratio
Very small activities of C-14
Rubidium-87 is used for rocks on Earth as the half-life of C-14 is too small

Question 30

Rubidium 87 half life

Answer 30

49 billion years