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physicsGCSE > p6 > Flashcards

p6 Flashcards

1
Q

what type of process is radioactivity?

A

random and unpreictable

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2
Q

what happens when nuclei are unstable?

A

emit
* alpha particles
* beta particles
* neutrons
* electromagneric radiation (gamma rays)

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3
Q

what is the effect of each radaition emited on the nucleus?

(mass and charge)

A
  • alpha particles
  • beta particles
  • neutrons
  • electromagneric radiation (gamma rays)
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4
Q

what happens when the photon has enough energy to completley remove an electron?

A

atom becomes ionised
provided by photons from gamma, X rays, Ultraviolet

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5
Q

what are the differences in contamination and irradiation?

A

contamination: radioactive material taken inside body/on skin, you become radio active
irradiation: radioactive material outside the body

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6
Q

what are the hazards associated with irradiation and contamination?

hazard threatnes life

A

hazard: ionising cells can damage the DNA inside your body causing cancer
* amount of exposure increases the risk of getting cancers

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7
Q

how to the hazards assoicated with radioactive material differ according to the half life?

during radiography, choosing a tracker

A
  • shorter half life- tracker will decay before they can use the gamma camera
  • longer half life- will continue to emit radiation for a long time, increasing the risk of cancer
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8
Q

How are nuclear radiations used in medicine?

gamma knife

A

gamma source, emit gamma rays taht damage the cancer cells and restrict their growth or kill them

moveable: reduces the radiation given to healthy tissues

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9
Q

Describe the charge of the atom

A

An equal number of protons and electrons, to Crete an overall charge of 0

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10
Q

What are ions

A

Different number of electrons

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11
Q

What are isotopes?

A

Different number of neutrons , but same element (atomic number)

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12
Q

What is a radio active substance?

A

A substance that becomes stable by emitting radiation

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13
Q

What are the 3 different forms of radiation, and their charge?

A

Alpha ➡️ 2+
Beta➡️ 1-
Gamma➡️ 0

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14
Q

Describe alpha radiation

A

A particle
2 protons and 2 neutrons
Heavily ionising
Stopped by paper/skin
Very slow because is heavy
Up to few cm range

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15
Q

Describe beta radiation:

A

A fast moving electron
Stopped by thin aluminium
Moderately ionising
Fast
Up to 1m

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16
Q

Describe gamma radiation

A

A wave
High energy electromagnetic waves
Travels at the speed of light
Lightly ionising
Stopped by thick lead
Unlimbered range in air

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17
Q

What decides the radioactivity a source can emit?

A

The heavier , the more likely it is to emit all three types

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18
Q

What happens during gamma decay?

A

The nucleus stays the same but inky loses energy

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19
Q

What happens during alpha decay?

A

The nucleus loses two protons and two neutrons, therefore the new nucleus has a lower amount of protons and neutrons

4
2

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20
Q

What happens during beta decay?

A

A neurones turns into one electron (ditches) and one proton (stays in the nucleus) . so neutron number (lower) -1 , but the proton number increases by one, so the top number (overall mass stays the same).

0
-1

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21
Q

What is half life?

A

The time taken for half of the unstable nuclei in a radioactive substance to decay.

Time taken for activity to half

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22
Q

What is activity?

A

The number of nuclei that decay every second

23
Q

How do you solve mass after half life ?

A

Time ➗half life =n
Amount ➗ 2^n

24
Q

How do you solve half life from a graph?

A

Go to mass ➗2
Find it on graph,
Do it again : should be the same value

25
Q

In what format are isotopes written?

A

‘Name’-‘mass number’

  • to distinguish between isotopes
26
Q

How would you wrote the nuclear equation of yeh alpha decay of a nucleus of uranium - 238

A
  1. Uranium 238 goes first (completely separate from the alpha side
  2. Immediately after an arrow
  3. On the right hand side write the alpha particle charge
  4. Complete the equation
27
Q

How do you calculate net decline as a ratio?

A

Decrease in activity ➗ original activity
Leave as a fraction

28
Q

How do you plot activity on a graph?

A

Divide the mass by 2
Now use the NEW mass to divide by 2

Plot each increment keeping the half life the same

29
Q

How are electrons arranged in atoms?

A

Electrons occupy energy levels , the different energy levels, are are different distances.

The lowest energy level is closest to the nucleus

30
Q

How do atoms absorb electromagnetic radiation?

A

Electrons in low energy levels, move up to a higher energy level by gaining energy
(The electrons excite to higher energy levels)

*electrons can be excited by absorbing electromagnetic radiation

31
Q

What are photons ?

A

Particles of light

32
Q

Do atoms electrons absorb all EM radiation?

A

No the incident EM radiation must be of an exact certain frequency (difference of energy level between shells)

33
Q

Describe excitation

A

1️⃣A single photon is absorbed entirely by a single electron
2️⃣the energy of the photon is directly proportional to the frequency of EM radiation
3️⃣if the energy of the photon exactly matches the difference in energy between the two levels , the electron will excite to a higher energy level

34
Q

What happens when atoms emit electromagnetic radiation?

A

As only a certain number of electrons are allowed to exist at any given energy level (2,8,8)

Therefore the electrons that have excited to higher energy levels, will de-excite to return to original energy levels.

As they de-excite , they emit energy as photons agian

35
Q

How do electrons de-excite

A

As de-excites may return to it’s original energy level . It can do this at once or in steps. Each time it de-excites , it emits the energy in the form of a photon of a given frequency.
The emitted photons are of lower energy, then that was absorbed

36
Q

What happens when a small nuclei is unstable VS when a large nuclei is unstable?

A

A small nuclei wil undergo radioactive decay.
Whereas a big nuclei will undergo nuclear fission (it would take too much time to get rid of energy)

37
Q

What is the definition of nuclear fission ?

A

The splitting of a larger parent nucleus into two smaller daughter nuclei, with the release of energy and neutrons

38
Q

Draw out a nuclear fission event

A

neutron required to start the reaction

39
Q

What is “nuclear waste “?

A

The two smaller daughter nuclei produced in the reaction are themselves unstable, and since they are unstable. However as they are small they become stable by undergoing radioactive decay

40
Q

What is a chain reaction?

A

A process in which neutrons are realised during a fission event , to go on to produce further fission events.

41
Q

What is a controlled chain reaction?

A

A reaction where only one neutron from each fission event is able to produce another fission event

42
Q

What are control rods?

A

Carbon rods , that absorb the surplus neutrons and only let one go, so that energy is generated at a steady rate,

43
Q

What is an uncontrolled chain reaction ?

A

Where every neutron from each fission event goes on to produce further fission events.
Energy is released at an exponential rate

44
Q

What is the definition of “nuclear fusion “?

A

The joint of two small parent nuclei into a larger daughter nucleus , with the release of energy.
* the one daughter nuceli is more stable than the othet two that made it

45
Q

What are the advantages of nuclear fusion ?

A

No radioactive waste is produced.
The fuel required is readily available in water (more sustainable)
Nuclear fusion produced a lot more energy than fission, per kg

46
Q

What are the disadvantages of nuclear fusion?

A

Building a fusion reactor is not viable , as more energy is required to make the nuclei overcome their repulsive forces, than is related from fusion

47
Q

Where does energy come from in fission and fusion ?

A

There is a difference in made between parent and daughter nuclei (parent has more mass)

*no change in mass number
Mass then transformed into energy

48
Q

What is Einstein’s energy equation ?

A
49
Q

can electrons de-exciting emmit gama?

A

no this an only be done in a nucleus: where the neutrons and proton are further arranged in their own energy levels, but since the enrgy in the nucleus is much greater, the emmit phototns of a higher frequnecy

50
Q

what happens to the chain reaction, if the radio active material is very small?

A
  • the reaction will only happen if there are enough nuclei around the first nuclei
  • if too small, the neutrons will escape and the reaction will stop
51
Q

what conditions are required for nuclear fusion?

A
  • high temperatures (nuclei are moving aroun enough)
  • high pressures (nuclei kept close enough to fuse)
52
Q

how do you measure radiation?

A
  • use a geiger counter
  • device that clicks whenever radiation enters it
  • each click is a tiny current produced when the radiation ionises the atoms of gas inside the tube
  • measures activity in becquerel (counters per second)
53
Q

what deicides how ionising a substance is?

A
  • how much enrgy is transfer to the substance
  • alpha particles transfer the most energy to the substance they are travelling through, that is why it has a shorter range

physicsGCSE (7 decks)

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