radiation

Question 1

what makes atoms unstable

Answer 1

unstable nucleus
- it’s an isotope (radioisotope)
- same no. protons diff no. neutrons

Question 2

how do atoms get stable

Answer 2

give out NUCLEAR radiation at random (decay)
give out ALPHA, BETA, GAMMA

Question 3

alpha

Answer 3

He⁴ ₂
2 protons + 2 neutrons
+2 charge
mass 4

Question 4

alpha absorbed by

Answer 4

paper/air

Question 5

alpha ionising power

Answer 5

STRONG
big mass knocks atoms off easily
attracts electrons off
looses KE quickly

Question 6

beta

Answer 6

e ⁰-₁
high speed electron
-1 charge
1/1800 mass

Question 7

beta absorbed by

Answer 7

aluminium

Question 8

beta ionising power

Answer 8

WEAK repels electrons off
smaller mass
loses KE less quicklt

Question 9

gamma

Answer 9

high frequency emag. wave
fastest - speed of light
0 charge
0 mass

Question 10

gamma absorbed by

Answer 10

thick lead or conceete

Question 11

gamma ionising

Answer 11

VERY WEAK
- has to hit directly
- no mass
- loses KE slowly

Question 12

magnetic field affect on radiation

Answer 12

DEFLECTS alpha / beta in opposite direction (oppositely charged)
no affect on gamma (no charge)

Question 13

background radiation

Answer 13

exists all around from natural sources (ground rocks space)
subtract from radioactive source

Question 14

ionise

Answer 14

knock electrons off other atoms
as soon as radiation ionises it loses KE
increase likelihood of ionising = smaller penetrating distance

Question 15

detect radiation

Answer 15

GM tube and counter
photographic film (clear>dark)

Question 16

why do unstable atoms decay

Answer 16

to become stable

Question 17

alpha decay

Answer 17

proton no. down 2
mass no. down 4
new element

Question 18

beta decay

Answer 18

proton no. up 1
mass no. SAME (neutron become proton and electron)
new element

Question 19

gamma decay

Answer 19

gives of gamma radiation (had too much energy)
no change to numbers
same element

Question 20

neutron radiation/ decay

Answer 20

eject a neutron
proton no. has no change
mass no. down 1
same element

Question 21

how to measure activity

Answer 21

gm tube and counter or rate meter

Question 22

becquerels

Answer 22

how many nuclei are decaying per second
1Bq = 1 decay per second

Question 23

half life

Answer 23

how long (average) it takes for the activity to go down by HALF - this is constant
or how long it takes for the number of unstable nuclei to go down by half
longer time irons out fluctuations due to random decay

Question 24

what fraction of the orrigional substamce is still unstable

Answer 24

1/2^no. half lives

Question 25

uses of radiation (medical)

Answer 25

destroying/ shrinking tumors - gamma (penetrates into body) - long 1/2 life dont replace regularly radioactive tracer for imaging - gamma (penetrates out body) - short wont cause damage to healthy cells sterilisation of surgical tools - gamma (penetrates through packaging) - long dont replace regularly

Question 26

uses of radiation (industrial)

Answer 26

smoke alarms - alpha (smoke can block particles) - long 1/2 life dont replace regularly thickness control - beta (paper) gamma(steel) can pass through - long dont replace regularly radioactive tracker for locating leaks - gamma (can penetrate out) - medium (long enough to measure short enought to not contaminate) carbon dating - beta - 5700 years (C-14) radioactive dating of rocks - fraction of unstable:stable isotopes - long

Question 27

dangers of radiation

Answer 27

irradiation contamination

Question 28

irradiation

Answer 28

- alpha/beta/gamma hits object - object doesnt becoe radioactive - can be vlocked with shielding - stops when source is removed

Question 29

contamination

Answer 29

- occurs if radioactive source is on or in the object - contaminated object will be radioactive as long as source is in/on it - once object is contaminated radiation cant be blocked from it - it can be very difficult to remove contamination

Question 30

+/- of contamination

Answer 30

+ isotopes can be ued as tracers + uses of short half life means exposure is limited + imaging can replace invasive surgery - isotopes may not go where wanted - can be difficult to remove - exposure can damage healthy cells

Question 31

radioactive waste

Answer 31

- daughter nuclei have a long 1/2 life + are very hot - difficult to dispose of so are placed in COOLING PONDS to absorb the heat and radiation - need to be safely stored for a long time till activity drops

Question 32

precautions to dispose radioactive waste

Answer 32

- strong/thick containers - not rust (dont leak) - stored securely - so terrorists cant steal - stored deep in water - not near water table (cant contaminate drinking water)

Question 33

fusion

Answer 33

2 light nuclei COMBINE to form large nucleus mass is lost - changes to energy - E = mc^2 - to overcome electrostatic repulsion between protons they move fast + close to fuse (increase temp + pressure) - this fuels stars

Question 34

fission

Answer 34

large nucleus SPLIT into 2 smaller nuclei (+2/3 neutrons) - slow moving neutron collides w nucleus - SPLINTS into 2 daughter nuclei (+2/3 neutrons) - energy released as KE of products - neutrons from one fission cause fission of another (chain reaction)

Question 35

nuclear reactor

Answer 35

- fuel rods, moderator, control rods, water, steam, electrical output nuclear(fuel) -> thermal(water) -(boils)-> KE(steam) -> KE(turbine) -> electrical

Question 36

fuel rods

Answer 36

contain U-235 nuclei - slow moving neutron collides w nucleus + splits it

Question 37

moderator

Answer 37

- neutrons release in fission are travelling too fast to cause split - slowed down by moderator GRAPHITE/WATER

Question 38

control rods

Answer 38

- if every neutron caused fission reactions would go out of control + cause explosion - control rods ABSORB NEUTRONS to slow reaction rate - lowered/raised to absorb more / less BORON