P7 Radioactivity

Question 1

What is the identity of (α)?

Answer 1

A helium nuclei

Question 2

What is identity of (β)?

Answer 2

Electrons

Question 3

What is the identity of (γ) ?

Answer 3

Electromagnetic radiation

Question 4

What is (α) stopped by?

Answer 4

Paper

Question 5

What is (β) stopped by?

Answer 5

1mm of aluminium

Question 6

What is (γ) stopped by?

Answer 6

Thick lead

Question 7

Range in air of (α)

Answer 7

About 5cm

Question 8

Range in air of β

Answer 8

About 1m

Question 9

Range in air of (γ)

Answer 9

Unlimited

Question 10

Relative ionisation of different types of radiation

Answer 10

α=very stong
β=strong
γ=weak

Question 11

What is meant by the activity of a radioactive source?

Answer 11

number of unstable atoms that decay per second (or rate of decay of unstable atoms in source)

Question 12

Explain why most alpha particles can pass through metal foil?

Answer 12

nucleus very small compared to atom

so most alpha particles don’t pass near enough to nucleus to be affected by it

Question 13

Explain what is meant by a nuclear chain reaction?

Answer 13

a sequence of induced fission events in which each event causes further fission events which in turn cause further fission events,
each fission occurs when nucleus of a fissionable atom absorbs a neutron and splits into two smaller fragment nuclei,
releasing several neutrons which can cause other fissionable nuclei to split

Question 14

Explain what would happen in a nuclear reactor is coolant fluid leaked out of the core?

Answer 14

reactor core overheats,

as energy still released from fuel rods

Question 15

Explain what would happen in a nuclear reactor if control rods were pushed further into the reactor core

Answer 15

control rods absorb more neutrons,
so number of fission events/second decreases,
so rate energy is released from fuel rods decreases

Question 16

What is meant by nuclear fusion?

Answer 16

process in which two small nuclei fuse to form a single larger nucleus, releasing energy

Question 17

Explain why 2 nuclei repel each other when they get close

Answer 17

any particles with same type of charge repel each other all nuclei positively charged,
so when two nuclei approach they repel each other

Question 18

Explain why they need to collide at high speed in order to fuse together

Answer 18

when two nuclei collide they only fuse together if sufficient Kinetic Energy to overcome force of repulsion between them,
so must collide at high speed to fuse

Question 19

Give 3 reasons why nuclear fusion is difficult to acheive in a reactor?

Answer 19

plasma containing nuclei to be fused at very high temperature so nuclei move fast enough to fuse,
plasma difficult to control at such high temperatures,
strong magnetic fields prevent plasma touching inside walls of container and losing internal energy

Question 20

What is a half life?

Answer 20

The amount of time taken for the amount of radiation emitted by a source by a half

Question 21

What is activity measured in?

Answer 21

Becquerels (Bq)