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Physics > Radioactivity and space > Flashcards

Radioactivity and space Flashcards

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1
Q

What makes an atom radioactive?

A

Normally isotopes - if the nucleus is unstable it will decay and give out radiation

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2
Q

Is there a way to know when a nucleus decays?

A

No, it’s random

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3
Q

What happens when a nucleus decays?

A

It releases radiation (alpha, beta or gamma)

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4
Q

What does nuclear radiation do?

A

Causes ionisation by bashing into atoms and knocking electrons off

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5
Q

Describe alpha particles

A

Helium nucleus, made up of 2 protons and 2 neutrons

Big, heavy and slow

Don’t penetrate far into materials and are stopped quickly

They bash into lots of atoms and knock electrons off before they slow down because they’re big. This creates ions (Most ionising)

They’re positively charged so they’re deflected by electric and magnetic fields

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6
Q

Describe beta particles

A

An fast moving electron which has been emitted from the nucleus when a neutron turns into a proton and an electron

So for every B-particle emitted, the number of protons in the nucleus increased by 1

Fast and small

Penetrate moderately before collision and are moderately ionising

Defected by electric and magnetic fields

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7
Q

Describe gamma rays

A

No mass, just energy (EM wave)

Penetrate a long way into materials without being stopped

Weakly ionising as they pass through instead of colliding, but eventually hit something and does damage

Not deflected by electric or magnetic fields as they have no charge

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8
Q

What stops each type of radiation?

A

Alpha particles - stopped by skin or paper

Beta particles - stopped by thin metal

Gamma rays - stopped by heavy lead

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9
Q

What is background radiation? Give examples

A

Radiation in every day life that everyone experiences

Unstable isotopes in food or air
Cosmic rays from the sun

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10
Q

Where is there higher levels of radiation and why?

A

At high altitudes, as cosmic rays are stronger

In mines as rocks radiate

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11
Q

What effect does radon have on people?

A

Radon could be trapped in a house depending on what rock the house was built on

It can increase lung cancer

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12
Q

What happens to activity as a whole when more nuclei decay?

A

The activity gets less so less radiation is emitted the older it is

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13
Q

What is half-life?

A

The time taken for half of the radioactive atoms present to decay

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14
Q

What does a short half life mean?

A

The activity falls quickly because lots of nuclei are dying quickly

A long half life means the opposite

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15
Q

The activity of a radioisotope is 640cpm (counts per minute). Two hours later it has fallen to 40cpm. Find the half life

A

It has halved 4 times

Four half lives = 2 hours

One half life = 30 minutes

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16
Q

How to measure a half life from a graph?

A

Take several readings and work it out

Remember if there’s background radiation to take away the background radiation first

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17
Q

How does radiation harm living cells?

A

Beta and gamma can penetrate the skin, getting inside and ionising cells
This damages the cells and could lead to cancer

Alpha can’t penetrate through the body but can be ingested and work in local area

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18
Q

What does really high levels of radiation do to your cells?

A

Kills them - this is radiation sickness

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19
Q

What are ways to protect yourself from radiation in a lab?

A

Never have skin contact

Keep the source at arm’s length to keep it away from the body

Point the source away from body and don’t look at it directly

Put it in a lead box

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20
Q

What are ways to protect yourself against nuclear radiation?

A

Full hazmat suits

Lead barriers and screens

Remote controlled arms to deal with sources

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21
Q

How are alpha particles used in every day life?

A

In smoke detectors
The radiation ionises the air and a current flows between two electrodes

If there’s a fire, the smoke absorbs the radiation, the current stops and the alarm sounds

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22
Q

How is beta radiation used in every day life?

A

They can be used as tracers

Put inside a body, they can be used to see if the patient’s systems are working properly as the radiation is monitored and taken around the body

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23
Q

How is gamma radiation used in every day life?

A

High doses can kill cells so can be used to treat cancer - but they have to be directly on the cancer cell to not harm any other cells

It can also sterilise medical equipment as they kill cells

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24
Q

How does radiation let us know the age of rocks?

A

Measuring the amount of a radioactive isotope left in a sample and knowing it’s half life you can work out how long it’s been around

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25
Q

Why is radioactive dating not accurate?

A

The radioactive isotopes being measured may not have always been constant throughout the years, therefore it could have more or less than it’s supposed to

Not all things do what we expect - some things could take more or less of an isotope than expected

The object could be contaminated

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26
Q

What is the order of the planets

A 
Mercury
Venus
Earth
Mars
(Asteroid belt)
Jupiter
Saturn
Uranus
Neptune
(Pluto)
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27
Q

Why is there an asteroid belt between Mars and Jupiter?

A

Leftovers from when the sun formed didn’t get to form a planet as Jupiter’s gravitational pull kept interfering

28
Q

What is a meteor and a meteorite?

A

A meteor is a piece of rock that comes into our planet and burns up (shooting star)

A meteorite is a meteor that hasn’t burnt up and falls to earth

29
Q

What are comets?

A

Balls of ice and dust which orbit the sun, slingshotting around it so they only come back in a very long time

As it approaches the sun it melts leaving a bright trail of gas and debris behind it

30
Q

What are NEOs?

A

Near earth objects such as asteroids and comets

These can create craters, ‘import’ unusual elements from space or wipe out species

31
Q

How does the earth protect itself against things in outer space? (Asteroids)

A

It has a magnetic field that attracts things away from it.

It’s like a giant bar magnet, but the south end is at the North Pole, as when you use a compass, North is attracted the the North Pole

32
Q

How does the earth protect against cosmic rays?

A

The sun releases gamma and X rays but the earth’s magnetic field and the ozone layer protects it

33
Q

How do solar flares affect us?

A

It can damage satellites and short circuit them due to the ionised particles from the sun

34
Q

Why are the Northern lights formed?

A

Solar flares can be carried down the magnetic poles towards either the north or South Pole

These ionised particles are transferred to particles in the air and cause them to emit light

35
Q

What is a galaxy?

A

A spiral of planets and stars (the Milky Way)

36
Q

What is a light year?

A

The distance light travels through a vacuum in one year

37
Q

How is a black hole formed?

A

When a big star has used up all its fuel it exploded and after, what’s left is very dense
Nothing can escape its gravitational pull

They have a very large mass but a tiny diameter

38
Q

How do scientists know a black hole is there?

A

They observe X rays emitted by other stars get sucked in

39
Q

What is the formation of a star?

A

Form from dust and gas

Gravity makes them spiral together to form a Protostar - gravitational potential energy is converted into thermal

When the temperature gets high enough, nuclear fusion happens in hydrogen nuclei to form helium nuclei and give out masses of heat and light
It is the main sequence star and can last several years because the outward pressure matches gravity

As the hydrogen runs out it becomes a red giant and the surface cools

It then branches off

40
Q

What happens after a big star becomes a red giant?

A

Big stars - explode into a supernova
The core of the supernova is very dense and is called a neutron star - if it’s big enough it will become a black hole

The dust thrown off of the supernova will form into a second generation stars like our sun. It will create a new solar system

41
Q

What happens when small stars become a red giant?

A

It cools and contracts into a white dwarf and finally becomes a black dwarf when the light fades completely

42
Q

How do we know the galaxies are moving away?

A

When looking at light from them, the frequencies are all lower than they should be (red-shift) suggesting that they’re moving away

This suggests the universe is expanding

43
Q

What is the theory of the Big Bang?

A

All the energy and matter in the universe was compressed, then it exploded

The expansion is still happening and by calculation it happened 14billion years ago

Without gravity, everything would keep expanding but because all the galaxies are attracted to one another, the universe is slowing down

44
Q

What are the two fates of the universe?

A

The Big Crunch - the universe would stop expanding and start contracting

Cold oblivion - there’s too little mass in the universe to stop the expansion so it expands forever

45
Q

What are the issues with sending people to space?

A

It would take ages to get to the destination

There’d have to be enough fuel, food, water and oxygen

It would be expensive

They’d have to remove toxic gases like CO2 from the air and protect them from cosmic waves

46
Q

What are the three types of unmanned probe missions?

A

Fly by - passes close by to record things such as temperature and radiation levels

Burn up - a probe enters the atmosphere, sends data back to earth then gets burnt up

Landing - rovers go and take photos on different planets (eg mars)

47
Q

What are the pros and cons of unmanned drones?

A

Pros - don’t need food or water
Can withstand lethal conditions
Cheaper and don’t have to be safe
Nobody gets hurt

Cons - can’t repair the ship
Can’t overcome simple problems

48
Q

What are the problems with space telescopes?

A

Earth’s atmosphere gets in the way of light, absorbing some

Light pollution makes it hard to pick out objects

49
Q

How do they get around light pollution with telescopes?

A

Be where there’s little light

Send a telescope into space - although repairs on this are hard to do

50
Q

What can EM wave telescopes do?

A

Radio telescopes need to be large but aren’t affected by the earth’s atmosphere and they let people observe objects too faint for light telescopes

X-ray telescopes can see violent, high temperature events like exploding stars but they only work from space as the earth’s atmosphere absorbs x-rays

51
Q

What’s the difference between fusion and fission?

A

Fusion is the joining of two nuclei to create a heavier nuclei, dispelling energy

Fission is he disintegration of a nucleus to create two nuclei and energy is released

52
Q

How does nuclear fission create a chain reaction?

A

When a nucleus separates, neutrons are given out which then go onto other atoms, splitting them.

Fission is then chained

53
Q

How do control rods control the amount of nuclear fission?

A

They absorb neutrons and can be raised or lowered

When lowered, they absorb more neutrons so it slows the rate of nuclear reactions.

54
Q

How is the energy from nuclear fission carried away?

A

In gamma rays

55
Q

How do nuclear generators work?

A

They do nuclear fusion or fission and release energy.

This energy heats water, turning it into steam to power turbines

56
Q

How does a nuclear explosion happen?

A

Uncontrolled chain reactions providing too much energy

57
Q

What gives more energy, fusion or fission?

A

Fusion

58
Q

What is irradiation?

A

Exposure to radiation

59
Q

What is the radiation dose and what is it measured in?

A

The risk of harm to body tissue

Measured in Sieverts (Sv)

60
Q

What is contamination of radioactivity?

A

Getting radioactive particles onto objects

61
Q

What are radioactive tracers?

A

Medical instruments that emit radiation can be put into the body

You can them track them through the body and see if anything is wrong (eg. Travel to the thorax and see if it absorbs the radiation at a rate it’s supposed to)

62
Q

In radiotherapy, why are the gamma rays shot at the tumour at various angles?

A

So the body cells around the tumour have little radiation whereas the tumour gets the full dose.

63
Q

When does a radioactive source reach zero radioactivity?

A

It never does

64
Q

What is radioactive activity measured in?

A

Becquerels (Bq)

65
Q

How can you change the half life of a sample?

A

You can’t

Physics (11 decks)

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