Radioactivity and space Flashcards
What makes an atom radioactive?
Normally isotopes - if the nucleus is unstable it will decay and give out radiation
Is there a way to know when a nucleus decays?
No, it’s random
What happens when a nucleus decays?
It releases radiation (alpha, beta or gamma)
What does nuclear radiation do?
Causes ionisation by bashing into atoms and knocking electrons off
Describe alpha particles
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
Describe beta particles
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
Describe gamma rays
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
What stops each type of radiation?
Alpha particles - stopped by skin or paper
Beta particles - stopped by thin metal
Gamma rays - stopped by heavy lead
What is background radiation? Give examples
Radiation in every day life that everyone experiences
Unstable isotopes in food or air
Cosmic rays from the sun
Where is there higher levels of radiation and why?
At high altitudes, as cosmic rays are stronger
In mines as rocks radiate
What effect does radon have on people?
Radon could be trapped in a house depending on what rock the house was built on
It can increase lung cancer
What happens to activity as a whole when more nuclei decay?
The activity gets less so less radiation is emitted the older it is
What is half-life?
The time taken for half of the radioactive atoms present to decay
What does a short half life mean?
The activity falls quickly because lots of nuclei are dying quickly
A long half life means the opposite
The activity of a radioisotope is 640cpm (counts per minute). Two hours later it has fallen to 40cpm. Find the half life
It has halved 4 times
Four half lives = 2 hours
One half life = 30 minutes
How to measure a half life from a graph?
Take several readings and work it out
Remember if there’s background radiation to take away the background radiation first
How does radiation harm living cells?
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
What does really high levels of radiation do to your cells?
Kills them - this is radiation sickness
What are ways to protect yourself from radiation in a lab?
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
What are ways to protect yourself against nuclear radiation?
Full hazmat suits
Lead barriers and screens
Remote controlled arms to deal with sources
How are alpha particles used in every day life?
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
How is beta radiation used in every day life?
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
How is gamma radiation used in every day life?
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
How does radiation let us know the age of rocks?
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
Why is radioactive dating not accurate?
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
What is the order of the planets
Mercury Venus Earth Mars (Asteroid belt) Jupiter Saturn Uranus Neptune (Pluto)
Why is there an asteroid belt between Mars and Jupiter?
Leftovers from when the sun formed didn’t get to form a planet as Jupiter’s gravitational pull kept interfering
What is a meteor and a meteorite?
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
What are comets?
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
What are NEOs?
Near earth objects such as asteroids and comets
These can create craters, ‘import’ unusual elements from space or wipe out species
How does the earth protect itself against things in outer space? (Asteroids)
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
How does the earth protect against cosmic rays?
The sun releases gamma and X rays but the earth’s magnetic field and the ozone layer protects it
How do solar flares affect us?
It can damage satellites and short circuit them due to the ionised particles from the sun
Why are the Northern lights formed?
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
What is a galaxy?
A spiral of planets and stars (the Milky Way)
What is a light year?
The distance light travels through a vacuum in one year
How is a black hole formed?
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
How do scientists know a black hole is there?
They observe X rays emitted by other stars get sucked in
What is the formation of a star?
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
What happens after a big star becomes a red giant?
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
What happens when small stars become a red giant?
It cools and contracts into a white dwarf and finally becomes a black dwarf when the light fades completely
How do we know the galaxies are moving away?
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
What is the theory of the Big Bang?
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
What are the two fates of the universe?
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
What are the issues with sending people to space?
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
What are the three types of unmanned probe missions?
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)
What are the pros and cons of unmanned drones?
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
What are the problems with space telescopes?
Earth’s atmosphere gets in the way of light, absorbing some
Light pollution makes it hard to pick out objects
How do they get around light pollution with telescopes?
Be where there’s little light
Send a telescope into space - although repairs on this are hard to do
What can EM wave telescopes do?
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
What’s the difference between fusion and fission?
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
How does nuclear fission create a chain reaction?
When a nucleus separates, neutrons are given out which then go onto other atoms, splitting them.
Fission is then chained
How do control rods control the amount of nuclear fission?
They absorb neutrons and can be raised or lowered
When lowered, they absorb more neutrons so it slows the rate of nuclear reactions.
How is the energy from nuclear fission carried away?
In gamma rays
How do nuclear generators work?
They do nuclear fusion or fission and release energy.
This energy heats water, turning it into steam to power turbines
How does a nuclear explosion happen?
Uncontrolled chain reactions providing too much energy
What gives more energy, fusion or fission?
Fusion
What is irradiation?
Exposure to radiation
What is the radiation dose and what is it measured in?
The risk of harm to body tissue
Measured in Sieverts (Sv)
What is contamination of radioactivity?
Getting radioactive particles onto objects
What are radioactive tracers?
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)
In radiotherapy, why are the gamma rays shot at the tumour at various angles?
So the body cells around the tumour have little radiation whereas the tumour gets the full dose.
When does a radioactive source reach zero radioactivity?
It never does
What is radioactive activity measured in?
Becquerels (Bq)
How can you change the half life of a sample?
You can’t
