Nuclear physics

Question 1

Einstein’s mass energy equation

Answer 1

E = mc²

Question 2

Why do individual nucleons have more energy than the mass of a nucleus

Answer 2

nucleons at high energy state have more mass

Question 3

A nucleus has a higher mass because of what energy

Answer 3

Binding energy

any extra energy is kinetic

Question 4

Mass defect

Answer 4

Difference between the total mass of individual nucleons and the mass of the nucleus when infinitely seperated

Question 5

Binding energy

Answer 5

Minimum energy required to separate nucleons to infinity

Question 6

How to find binding energy per nucleon

Answer 6

• find mass defect
• use Einstein’s equation to find the energy
• Divide the energy change by the number of nucleons

Question 7

What is the binding energy of a neutron

Answer 7

Zero because it is a lone nucleon

Question 8

Radioactive decay

Answer 8

Random and spontaneous disintegration process where a nucleus emits ionising radiation such as alpha, beta and gamma rays

Question 9

Radioactive decay constant

Answer 9

Probability of the decay of a nucleus per unit time

unit s^-1

Question 10

Atomic mass unit

Answer 10

1/12 of the mass of a neutral atom of carbon-12

Question 11

Mass excess

Answer 11

Mass in u minus the nucleon number

Question 12

Nuclear fission

(3)

Answer 12

A single large nucleus divides to form smaller nuclei

• initiated by neutron bombardment
• binding energy per nucleon increases

Question 13

Nuclear fusion

(3)

Answer 13

Two light nuclei combine to form a single mroe massive nucleus
- initiated by very high temperatures
- release energy

Question 14

Decay constant

Answer 14

Probability that an individual nucleus will decay per unit time interval

Question 15

Activity definition

Answer 15

rate at which the nuclei decay/ disintegrate.

unit is becquerel

Question 16

Activity formula

Answer 16

A= -λN
A= ∆𝑁/ ∆t

Question 17

why is radioactive decay random

2 marks

Answer 17

• time at which a nucleus will decay cannot be predicted
• constant probability of a decay of each nucleus in the sample

Question 18

why is radioactive decay spontaneous

2 marks

Answer 18

• the decay is not influenced by external factors
• the decay of a particular nucleus is not affected by the presence of other nuclei

Question 19

Half life

Answer 19

Time taken for activity of sample to halve

Question 20

Number of decayed nuclei, count rate and activity of a sample can be given by:

N, R, A

Answer 20

x = x0^e–λt

Question 21

Half life formula in terms of decay constant

Answer 21

= ln2/λ

Question 22

Charge of a beta particle

Answer 22

4e

Question 23

Charge of an alpha particle

Answer 23

2e

Question 24

A radioactive element has a half life of 4 hours. Explain why its mass and activity cannot be used to determine its half life

Answer 24

Sample would decay appreciably whilst measurements are being made