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Physics > P8 > Flashcards

P8 Flashcards

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1
Q

Define radioactive decay (3)

A

process when unstable nuclei “decay”

emit particles or waves to form more stable nuclei

occurs spontaneously + randomly over time

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2
Q

What does a radioactive nucleus emit when it decays (3)

A

alpha particles

beta particles

gamma rays

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3
Q

Define ionising radiation (2)

A

stream of radioactive rays/particles

has enough energy to cause other atoms to lose electrons + become cations

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4
Q

Detection of Radioactivity

A

Geiger-Muller tube

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5
Q

Alpha particle description

A

positively charged particle

has two protons + two neutrons

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6
Q

Alpha particle penetration (2)

A

4-10 cm of air

stopped by sheet of paper

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7
Q

Alpha particle electric charge

A

+2

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8
Q

Alpha particle relative atomic mass

A

4 atomic units

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9
Q

Alpha particle ionising effect

A

strongly ionising

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10
Q

Alpha particle effects of magnetic/electric field

A

weakly deflected in opposite direction to beta

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11
Q

Use of alpha particles (5)

A

smoke detectors

radiation produces ions in air

ions conduct electric current

smoke absorbs some of alpha particles = reduces ion number + current

sets off alarm

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12
Q

Beta particle description

A

high energy electron from a nucleus

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13
Q

Beta particle electric charge

A

-1

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14
Q

Beta particle relative atomic mass

A

1/1860th of an atomic unit

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15
Q

Beta particle penetration power (2)

A

1 m of air

stopped by few mm of aluminum

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16
Q

Beta particle ionising effect

A

weakly ionising

17
Q

Beta particle effect of magnetic/electic field

A

strongly deflected in opposite direction to alpha

18
Q

Gamma ray description

A

high energy/short-wavelength electromagnetic wave released from an atom

19
Q

Gamma ray electric charge

A

electrically neutral

20
Q

Gamma ray relative atomic mass

A

no atomic mass

21
Q

Gamma ray penetrative power (3)

A

strong penetration at speed of light

no material can completely stop it

strength can be reduced by several cms of lead + metres of concrete

22
Q

Use of beta particles (2)

A

medical tracers - checking thickness of material

number of beta particles passing through material is reduced when thickness is increased

23
Q

Ionising effect of gamma rays

A

weakly ionising

24
Q

Magnetic/electric field effect on gamma ray

A

unaffected

25
Q

Use of gamma rays

A

medical industry - sterilisation of medical equiptment + to treat cancer

26
Q

Define background radiation

A

radiation from artificial + natural sources

27
Q

What is meant by radiation being ionising

A

radiation collides with atom –> removes electrons from atom causing it to become charged

28
Q

What happens when a nucleus emits an alpha particle

A

loses 2 protons

nucleon number decreases by 4

29
Q

What happens when a nucleus emits a beta particle (3)

A

proton number increases by 1 - 1 neutron changes to proton

gains 1 electron

electron emitted as beta particle

30
Q

What happens when a nucleus emits a gamma ray (2)

A

wave carrying energy is emitted

no change to proton or necleon number

31
Q

Define half-life (2)

A

time taken for half the radioactive nuclei to decay

measured in becquerels

32
Q

Define becquerels

A

1 becquerel = 1 nucleus decay and emits radiation per second

33
Q

Dangers of alpha particles (2)

A

dangerous to human tissue - strong ability to ionise other particles

cannot penetrate skin

34
Q

Dangers of gamma radiation (2)

A

high penetrating power

cell has repair mechanisms that make ordinary levels of gamma radiation harmless

35
Q

Safety precautions when handling radiation (4)

A

forceps when moving radioactive sources

not pointing radioactive sources at living tissue

store radioactive material in lead containers

check surrounding for radiation level above background level

36
Q

Example of radioactive iodine to treat cancer in thyroid (2)

A

thyroid cells absorb more iodine than other body parts

iodine absorbed by cancer cells which kills them

37
Q

Define radiotherapy

A

radiation fired at cancer cells to kill them

38
Q

Define radioactive carbon dating (3)

A

carbon contains small amount of radioactive isotope carbon-14 (half-life of 5700 years)

living material dies = carbon-14 will decay

ratio of carbon-14 nuclei to non-radioactive carbon-12 can calculate age

Physics (3 decks)

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