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radiation Flashcards

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1
Q

what makes atoms unstable

A

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

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2
Q

how do atoms get stable

A

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

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3
Q

alpha

A

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

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4
Q

alpha absorbed by

A

paper/air

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5
Q

alpha ionising power

A

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

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6
Q

beta

A

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

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7
Q

beta absorbed by

A

aluminium

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8
Q

beta ionising power

A

WEAK repels electrons off
smaller mass
loses KE less quicklt

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9
Q

gamma

A

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

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10
Q

gamma absorbed by

A

thick lead or conceete

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11
Q

gamma ionising

A

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

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12
Q

magnetic field affect on radiation

A

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

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13
Q

background radiation

A

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

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14
Q

ionise

A

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

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15
Q

detect radiation

A

GM tube and counter
photographic film (clear>dark)

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16
Q

why do unstable atoms decay

A

to become stable

17
Q

alpha decay

A

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

18
Q

beta decay

A

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

19
Q

gamma decay

A

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

20
Q

neutron radiation/ decay

A

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

21
Q

how to measure activity

A

gm tube and counter or rate meter

22
Q

becquerels

A

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

23
Q

half life

A

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

24
Q

what fraction of the orrigional substamce is still unstable

A

1/2^no. half lives

25
Q

uses of radiation (medical)

A

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

26
Q

uses of radiation (industrial)

A

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

27
Q

dangers of radiation

A

irradiation
contamination

28
Q

irradiation

A
  • alpha/beta/gamma hits object
  • object doesnt becoe radioactive
  • can be vlocked with shielding
  • stops when source is removed
29
Q

contamination

A
  • 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
30
Q

+/- of contamination

A

+ 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

31
Q

radioactive waste

A
  • 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
32
Q

precautions to dispose radioactive waste

A
  • 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)
33
Q

fusion

A

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

34
Q

fission

A

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)

35
Q

nuclear reactor

A
  • fuel rods, moderator, control rods, water, steam, electrical output
    nuclear(fuel) -> thermal(water) -(boils)-> KE(steam) -> KE(turbine) -> electrical
36
Q

fuel rods

A

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

37
Q

moderator

A
  • neutrons release in fission are travelling too fast to cause split
  • slowed down by moderator
    GRAPHITE/WATER
38
Q

control rods

A
  • 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

physics (19 decks)

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