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Physics > Section 3 - Radioactivity and Astronomy > Flashcards

Section 3 - Radioactivity and Astronomy Flashcards

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1
Q

What is the solar system?

A

all the stuff that orbits our sun

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2
Q

What is included in the solar system?

A

Planets, Dwarf planets, Moons, Artificial satellites, Asteroids, Comets

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3
Q

Planets

A

Large objects that orbit a star.

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4
Q

What are the 8 planets in our solar system?

A

(from the sun, outwards)
Mercury, Venus, Earth, Mars, Jupiter, Saturn,Uranus, Neptune

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5
Q

Dwarf Planets

A

Planet like objects that arent large enough to be planets.

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6
Q

Moons

A

Orbit planets wiht almost circular orbits, natural sattelites

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7
Q

Asteroids

A

Lumps of rock and metals that orbit the sun, they are usually found in the asteroid belt

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8
Q

Comet

A

Lumps of ice and dust that orbit the sun. highly eliptical orbits

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9
Q

What is alpha radiation

A

Alpha radiation is when an alpha particle is emmitted fromthe nucleus (2 protons and 2 neutrons)

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10
Q

How far do alpha particles travel?

A

Few cm in air and stopped by thin paper because they are strongly ionising

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11
Q

How are B- particles created

A

when a neuton decays into an electron and a proton. That electron is then thrown out of the nucleus

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12
Q

How far do B- particles travel?

A

Few meters and absorbed by a sheet of aluminium, moderately ionising

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13
Q

How are gamma rays created?

A

A neucleus decaying and releasing energy in form of gamma rays

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14
Q

How far do gamma rays go

A

A very long distance, can penetrade deeply into materials, weakly ionsiing. Cna be stopped by lead or meteres fo cncrete

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15
Q

When can an electron move up energy levels/shells?

A

if it absorbs EM radiation with the right amount of energy

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16
Q

What happens when an electron moves up to a higher energy level?

A

It moves up to a partially filled shell or empty and is said to be “exited”
It then quickly falls back to its original energy level

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17
Q

What happens when an exited electron falls back to its original energy level?

A

It will emit the same amount of energy it absorbed, this energy is carried away by EM radiation

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18
Q

What happens to electron shells as they move further out?

A

They get closer togethe, so the differrence in the energy levels between the shells gets smaller

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19
Q

What is a positron?

A

An anti-electron
Same mass, positive charge

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20
Q

Why is a positron made?

A

When a nucleus have too few neutrons, a proton will turn into a neutron and emit a fast-moving positron

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21
Q

What is a Becquerel?

Bq

A

1 decay per second

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22
Q

How is radioactive decay mesured?

A

In a geiger-muller tube

23
Q

Half -life

A

The average time taken for the number of radioactive nuclei in an isotope to halve

24
Q

Backround radiation

A

The low level radiation thats around us all the time

25
Q

What are the 3 main exposures to backround radiation?

A

Naturally occuring isotopes - air, some foods, buildings and rocks
Space - Cosmic rays from the sun most blocked by the atmosphere
Human activity - fallout from nuclear explosions

26
Q

What is exposure to radiation called?

A

Irradiation

27
Q

How to prevent irradiation

A

Keeping sources in lead-lined boxes/ standing behind barriers or different room.

28
Q

Contamination

A

Unwanted Radioactive particles getting onto objects

29
Q

How can radioactive contamination be harmfull?

A

if touching the object without gloves, you would them become contaminated. If the atoms may then decya, causing you harm

30
Q

Ionisation

A

Radiation can enter living cells and ionise atoms and molecules within them leading to tissue damage

31
Q

Hazard correlation with half-life

A

The lower the activity of a radioactive source, the safer it is to be around.
Longer half life = more dangerous

32
Q

Uses of Alpha Radiation

A

Household fire alarms
Smoke absorbs small particles so when alpha radiation is no lenger detected, the alarm goes off.

33
Q

Uses of Gamma Rays

A

Food and Equipment sterilisation
Gamma rays kill microbes
Food can be irradated

34
Q

Uses of General Radiation

A

Tracers and thickness gauges
Some radiation can be injected into a patient and tracked by an external detector. - Used to detect and diagnose certain medical conditions e.g. cancer
The tracers have to be BETA OR GAMMA so they can pass through and out the body without causing too much damage.

35
Q

Uses of Beta Radiation

A

Thickness gauges
e.g paper. Detector sense how much radiation gets through, when this changes the thickness has changed.

36
Q

What does PET stand for

A

Positron emission tomography

37
Q

What is a PET scan used for

A

To show tissue or organ function and can be used to diagnose medical conditions.

38
Q

How can PETs diagnose cancer cells?

A

It can identify active tumors by shwoing metabolic activity in tissue. Cancer cells havea much higher metabolic activity therefore can be identified.

39
Q

How do PET scans work?

A
  1. Inject a sustance used in the body with a positron-emitting radioactive isotope with a short half used as a tracer.
  2. Positrons emmited by the isotope meet electrons in an organ and annihilate emmiting high energy gamma ray
  3. Distribution of radioactivity = metabolic activity
40
Q

How does radiation therapy work?

A

Particles are injected near a tumor and kill the cells

41
Q

Nuclear Fission

A

A type of nuclear reaction used to release energy from uranium or plutonium.

42
Q

Chain reaction in nuclear fission

A
  1. a slow-moving neutron is fired at a large unstable nucleus
  2. this neutron is absorbed by the nucleus, making it more unstable, causing it to split
  3. The split atom forms 2 lighter daughter cells and energy is released.
  4. Some neutrons will be spit out in the reaction, moving into other large unstable nuclei, causing a chain reaction
43
Q

Describe the energy transferrs in a nuclear power station

A

Energy relesed by fission is transferred to the thermal energy store of the moderator, then to the coolant, then to the cold water passing through the boiler. This causes the water to boil and the energy to be transferred to its kinetic energy store.
This then goes to a turbine, then a generator.

44
Q

Centripedal force

A

Centre seeking force

45
Q

What is the first stage of a star forming?

A

Stars initially form a cloud of dust and gas called a nebula

46
Q

What is the second stage of a star forming?

A

The force of gravity pulls the dust and gas together to form a protostar. The temperature rises as the star gets denser and more particles collide with each other. When the temp gets high enough, hydrogen nuclei undergo nuclear fusion to form He nuclei. This gives out huge amounts of energy, which keeps the core of the star hot.

47
Q

What is the third (main sequence) stage of a star forming?

A

The star enters a long stable period. During this, the outward pressure caused by thermal expansion balances the force of gravity, pulling everything inwards. This is called a main sequence star and typically lasts several billion years. The heavier the star, the shorter this time.

48
Q

What is the fourth stage of a star forming?

A

Eventually, the H in the core begins to run out and the force due to gravity is larger than the pressure of thermal expansion. The star is compressed until it is dense and hot enough that hydrogen in its outer layers and helium in its core can undergo fusion; increasing pressure of thermal expansion - making the outer layers of the star expand

49
Q

What is Thermal Expansion?

A

The energy produced by nuclear fusion tries to expand a star

50
Q

What does the star form into after the fourth stage?

A

red giant (small star)
red supergiant (big star)
the outer surface gets red because it cools down

51
Q

What does a red dwarf form after?

A

A white dwarf
- A small to medium sized star like the sun then becomes unstable and ejects it outer layer of dust and gas. This leaves behind a hot, dense solid core.

52
Q

What do bigger stars form after red supergiant?

A

Big stars, start to glow brightly again as they undergo more fusion to make heavier elements. They expand and contract several times, as the balance between gravity and thermal expansion shifts. Eventually, they explode into a supernova.

53
Q

What can supernovas form?

A

Neutron stars or black holes
- the exploding supernova throws the outer layer of dust and gas into space, leaving a very dense core called a neutron star.
- If the star is massive enough, it will collapse and form a black hole

54
Q

What is a black hole?

A

A super dense point in space that not even light can escape from.

Physics (7 decks)

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