Unit 7 - Radioactivity

Question 1

define contamination

Answer 1

non radioactive material gets in contact with radioactive material

(radioactive material must get in touch)

Question 2

define irradiation

Answer 2

Exposure to nuclear radiation. The irradiation stops when
the source is removed or blocked.

Question 3

describe the nature of an alpha particle meaning physical representation

Answer 3

2 protons 2 neutrons
helium nucleus

Question 4

describe the nature of a beta particle

Answer 4

electron

Question 5

describe the nature of a gamma particle

Answer 5

electromagnetic wave

Question 6

in practice question- explain why fruits irradiated with amma radiation are safe to eat

Answer 6

• fruits are not radioactive
• fruits are not in contact with radioactive source
• fruits are not contaminated

Question 7

what is meant by nucleon number / mass number

Answer 7

the protons + the neutrons in the nucleus of an atom

Question 8

imp question- define isotopes

Answer 8

isotopes have the same atomic number but different mass number`

Question 9

define ioniasation

Answer 9

removal of electrons from an atom

Question 10

what is meant by alpha decay

Answer 10

the emision of an alpha particle from an unstable nucleus

Question 11

define radioactivity

Answer 11

The production of ions by radioactivity due to the energy transferred

Question 12

what is meant by atomic number or proton number

Answer 12

The number of protons in the nucleus of an
atom

Question 13

what is background radiation

Answer 13

The nuclear radiation from natural and artificial sources in our everyday environment

Question 14

name some sources of background radiation

Answer 14

• building rays
• cosmic rays (from stars)
• hospitals
• radon gas from the earth

Question 15

define half-life

Answer 15

time taken for a sample of radioactive material to have half of its atoms decayed

Question 16

what is the charge of an alpha particle

Answer 16

+2

Question 17

what is the charge of a beta particle

Answer 17

-1

Question 18

what is the charge of a gamma

Answer 18

neutral as it is a wave

Question 19

describe the penetration abilities of alpha

Answer 19

very low penetration ability
can be stopped by a sheet of paper

Question 20

describe the penetration abilities of beta

Answer 20

stronger penetration compared to alpha
can be stopped by 3mm of Al sheet

Question 21

describe the penetration abilities of gamma

Answer 21

very strong penetration ( more than alpha and beta)
can be stopped by several meters of concrete / which will absorb more gamma ray

Question 22

name a device used to detect radiation

Answer 22

GM tube

Question 23

explain the condition needed for nucleur fission

Answer 23

• high temperature required
• to increase KE of nuclei
• high pressure required
• because nuclei need to be close enough to collide
• since nuclei repel each other so to overcome the electrostatic forces of repulsion

Question 24

the energy released by the fision process starts in the nuclear store of the uranium atom. describe the transfers that occur after that

Answer 24

1. nuclear store of uranium
2. KE store of fision products
3. thermal store of graphite a gas
4. thermal store of water
5. KE of turbine
6. electricity by generator

Question 25

how is boron used in a nuclear reactor

Answer 25

control rod

Question 26

what does a control rod do

Answer 26

absorb neutrons and stop chain reaction

Question 27

use of uranium in nuclear reactor

Answer 27

fuel rod

Question 28

function of fuel rol

Answer 28

provide nuclei for fision reaction

Question 29

use of concrete / lead in nuclear reactor

Answer 29

sheilding
contains water that absorb neutrons ( for safety )

Question 30

what is grpahite used for in nuclear reactor

Answer 30

moderator

Question 31

function of moderator

Answer 31

slow down the fast neutrons from one fision reaction so they can be absorbed

Question 32

explain why background radiation is not always the same

Answer 32

radiation is random

Question 33

define chain reaction

Answer 33

When neutrons from the fission of one uranium nucleus are allowed to cause fission in more uranium nuclei, which
release more neutrons to continue the process