Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A LEVEL PHYSICS > Nuclear physics > Flashcards

Nuclear physics Flashcards

1
Q

how was the alpha scattering experiment setup?

A
  • alpha particles used as projectiles to study the structure of gold atoms
  • a very thin gold foil was used as the target for the alpha particles
    -a fluorescent screen was used as the detector, when alpha particles struck the screen a flash of light was produced allowing the team to see the trajectories
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what was the alpha scattering experiment measuring?

A
  • the number of alpha particles deflected by an angle theta
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

why did the apparatus have to be evacuated?

A
  • to stop the alpha particles being stopped by air
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what was the first Rutherford conclusion?

A
  • atom has a very small positively charged nucleus
  • responsible for the repulsion force on the positively charged alpha particle, causing it to change direction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what was the second Rutherford conclusion?

A
  • nucleus contains nearly all the mass of the atom
  • conservation of momentum explains this

MaVa + Mn x 0 = MaVa

nucleus barely moves after repulsion of a particles so Mn>Ma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what was the closest distance of approach?

A
  • minimum distance an alpha particle can get to the nucleus before being repelled due to Coulombs Force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what was the equation for closest distance of approach?

A

kinetic energy at start = potential energy at repulsion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what was electron scattering

A
  • experiment used to study the structure of matter
  • high energy electron beams fired at a target
  • deflection was analysed giving conclusions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the three equations for electron scattering?

A

lambda = h / p

p = E / c

sin theta = 1.22 lambda / d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is meant by an empirical equation?

A
  • an equation based entirely on experimental results
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what was the empirical equation for radius of nucleus?

A

R = Ro x A^1/3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

derive how i can plot this graph

A

R = Ro x A^n

ln R = lnRo + lnA^n

ln R = n lnA + lnRo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

whats the equation for nuclear density

A

p = 3/(4piR^3) x m

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is radiation?

A
  • when an unstable nuclei emits energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

give the nature of each three types of radiation

A

alpha particle - helium nucleus

beta particle - fast electron

gamma ray - electromagnetic photon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

give the charge of each of the three types of radiation

A

alpha particle is +2e

beta particle is -e

gamma ray is 0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

give the masses of each of the three types of radiation

A

alpha particle - 6.6x10^-27kg

beta particle - 9.1x10^-31kg

gamma ray - 0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

give the speed of each of the three types of radiation

A

alpha particle - 5% of c

beta particle - 98-99% of c

gamma ray - c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

give the ions per mm of air for a particle of 3MeV

A

alpha particle - 10000

beta particle - 100

gamma ray - 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

give the detection for each of the three types of radiation

A

alpha particle - slight deflection in electric and magnetic fields

beta particle - significant deflection in electric and magnetic fields

gamma ray - no deflection in electric and magnetic fields

all affects photographic film

21
Q

give the ionisation of each of the three types of radiation

A

alpha particle - strongly ionising

beta particle - much less ionising than a particles

gamma ray - very weakly ionising

22
Q

how does the charged gold leaf electroscope illustrate the strong ionising power of alpha radiation?

A
  • alpha particles create a large number of positive and negative ions in the air
  • the charge of the electroscope becomes neutralised depending on the inital charge
    ( free electrons attracted if positively charged )
    ( positive ions attracted if negatively charged )
  • as the charge on the electroscope is reduced, the gold leaf gradually collapses
23
Q

what is background radiation?

A

there is always radiation present in the environment, such as rocks that contain radioactive uranium

the sun also emits protons which can create ions in the atmosphere

24
Q

how does a smoke alarm work?

A
  • alpha particles ionise the air between plates so a current flows
  • smoke particles absorb the alpha particles so the air is no longer ionised and current decreases
  • this sets off the alarm
25
Q

describe the emission of radiation from a nucleus

A
  • the emission is both random
    and spontaneous
26
Q

what is the decay constant?

A
  • probability of a nucleus decaying per unit time
27
Q

what is the significance of the minus sign in the equation

A
  • the number of radioactive nuclei in a sample of material decreases with time
28
Q

what is the activity of a radioactive source

A
  • the number of disintegrations per second
29
Q

give the equation to predict the number of nuclei at any time

A

N = No x e^-kt

where k = decay constant

30
Q

what is half life

A
  • one half life is the time taken for half of a sample of radioactive nuclei to decay
31
Q

how is half life connected to the decay constant?

A

T1/2 = ln2 / decay constant

32
Q

what can the half life of a radioactive nucleus be used for?

A
  • dating of objects
  • medical diagnosis
33
Q

how does dating of objects work?

A
  • nuclei with long half lifes such as carbon 14 can be used to date organic objects
  • done by measuring the current amount of carbon-14 and comparing it to the initial amount
34
Q

how does medical diagnosis work

A
  • nuclei with relatively short half-lives are used as radioactive tracers in medical diagnosis
  • eg pure gamma emitters, half life of 6 hours, short enough to limit exposure but long enough for tests to be carried out
35
Q

why do radioactive nuclei have to be stored in a certain way

A
  • to prevent nuclei from damaging the environment and the people that may be living around them hundreds of years into the future
36
Q

what is meant by electron capture?

A

when an unstable nucleus absorbs one of its own orbiting electrons, to stabilise itself

37
Q

why can electromagnetic radiation be given off sometimes when decaying

A

the daughter nucleus may be excited

38
Q

what are the two ways in which i can take safety precautions when dealing with radioactive sources?

A
  • minimise time of exposure
  • keep as big a distance between you and the source
39
Q

what is nuclear stability

A
  • nucleus held together by strong force
  • protons experience a force of repulsion
  • if forces are out if balance, nuclei will become unstable
40
Q

what decay occurs if a nuclei has too many neutrons?

A
  • beta minus
41
Q

what decay occurs if a nucleus has too many protons

A

beta plus

electron capture

42
Q

what decay occurs if a nucleus has too many nucleons?

A
  • alpha decay
43
Q

what happens if a nucleus has too much energy

A

it will decay and emit a gamma ray

44
Q

what is the equation linking count and area

A

( area / surface area ) x count rate

45
Q

why us technetium used in medicine

A
  • metastable isotope, so it emits gamma rays to become more stable
  • physical half life is short
46
Q

what are the dangers of nuclear radiation , alpha radiation

A
  • outside body does little harm
  • inside body very dangeous
  • never used for medicine as danger of inhaling / digesting
47
Q

what are the dangers of beta radiation

A
  • more penetrating than alpha radiation
  • able to penetrate inside and outside the body
48
Q

what are the dangers of gamma rays?

A
  • in high doses, dangerous in and outside the body
49
Q

how does a Geiger tube work

A
  • radiation interacts with gas knocking off electrons
  • electrons are accelerated towards the anode via e field
  • as the electron accelerates it collides into more gas molecules, causing more ionisation
  • avalanche creates a sudden surge of current, detected as a pulse of electricity
  • pulse corresspondes to a single ionising event
  • external circuit count pucks up number of times

A LEVEL PHYSICS (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions