6. Nuclear Physics

Question 1

What are ‘radioactive’ substances?

Answer 1

Substances which give out radiation from the nuclei of their atoms, all the time, whatever is done to them

Question 2

What is background radiation and where does it come from?

Answer 2

It is radiation that is constantly around us
It comes from:
Natural sources such as rocks and cosmic rays from space
Man made sources such as fall out from nuclear tests and accidents

Question 3

What is an Alpha particle?

Answer 3

Two neutrons and two protons, it is the same as a Helium nucleus

Question 4

What is a Beta particle?

Answer 4

An electron from the nucleus

Question 5

What is a Gamma radiation?

Answer 5

Electromagnetic radiation from the nucleus

Question 6

Which substance ionises the most powerfully?

Answer 6

Beta then alpha

Gamma waves not deflected by electric or magnetic fields

Question 7

How penetrative is alpha radiation?

Answer 7

Not very it can be blocked by paper

Question 8

How penetrative is Beta radiation?

Answer 8

It can pass through paper but not aluminium

Question 9

How penetrative is Gamma radiation?

Answer 9

Very can pass through aluminium but is blocked by lead

Question 10

If the radioactive source is inside the body:

Answer 10

Alpha radiation is the most dangerous because it is easily absorbed by cells
Beta and gamma radiation are not as dangerous because they are less likely to be absorbed by a cell and will usually just pass right through it

Question 11

If the radioactive source is outside the body:

Answer 11

Alpha radiation is not as dangerous because it is unlikely to reach living cells inside the body
Beta and gamma radiation are the most dangerous sources because they can penetrate the skin and damage the cells inside

Question 12

What is the definition of half-life?

Answer 12

The average time it takes for the number of nuclei of the isotope in a sample to halve
The time it takes for the count rate from a sample containing the isotope to fall to half its initial level

Question 13

What is nuclear fusion?

Answer 13

Nuclear fusion is the joining of two atomic nuclei to form a larger one
Nuclear fusion is the process by which energy is released in stars

Question 14

What do Nuclear Fusion reactions release?

Answer 14

Huge amounts of energy

However not currently a viable method for generating power on Earth

Question 15

What is one use of alpha radiation?

Answer 15

It is used in smoke alarms
When there is a lot of smoke, the smoke absorbs the radiation so it doesn’t reach the detector and the alarm is triggered

Question 16

What is one use of Beta radiation is used in industry?

Answer 16

It is used to keep the thickness of paper correct during manufacturing

Question 17

What is nuclear fission?

Answer 17

Nuclear fission is the splitting of an atomic nucleus, into smaller nuclei and neutrons

Question 18

What substances are used in Nuclear reactors?

Answer 18

Uranium 235 and plutonium 239

Question 19

What is the life cycle of stars the same size as our sun?

Answer 19

Protostar
Main sequence star
Red giant 
White dwarf
Black dwarf

Question 20

What is the life cycle of stars much bigger than our sun?

Answer 20

Protostar
Main sequence star
Red super giant 
Supernova
Neutron star / Blackhole

Question 21

When are stars formed?

Answer 21

When enough dust and gas from space is pulled together by gravitational attraction
Smaller masses may be attracted by larger mass to become planets

Question 22

Why are main sequence stars stable?

Answer 22

Because the outward force of fusion is balanced by the inward force of gravity

Question 23

When does the main sequence star come around?

Answer 23

When the Hydrogen nuclei begin to fuse together

Question 24

What happens when a main sequence star runs out of fuel?

Answer 24

It’s inner core collapses and the outer layers swell and cool
It then either becomes a red giant or red super giant