- Created by: Jess
- Created on: 26-02-12 13:19
Nuclear radiation causes ionisation.
Ionisation = when an atom loses/gains electrons turning it into an ion.
When an unstable nucleus decays, it gives off one or more types of radiation. Alpha, beta or gamma are all types of radiation that can cause ionisation.
POSITIVE�ions form when�atoms LOSE electrons
NEGATIVE ions form when atomes GAIN electrons
ionisation can initiate chemical reactions between different atoms. When radiation enters human cells, it can ionise and damage�DNA. These can cause mutations and lead to cancer.
High doses of radiation can kill cells completely.
the further the radiation can penetrate before hitting an atom, the less ionising it is.���
Alpha, Beta & Gamma
Alpha particles = big & heavy.
Alpha radiation�= least penetrating/strongly ionising
�It can be stopped (or absorbed) by a sheet of paper.
Beta particles = small & fast electrons
Beta radiation = slightly penetrating/slightly ionising
It can be stopped by a few mm of aluminium
Gamma radiation occurs when the nucleus needs to get rid of more energy after giving off alpha & beta. It does this by emitting a gamma ray (EM radiation).��������� Gamma rays have no mass or charge.�������������������������������������������������������������������� Gamma = highly penetrating/weakly ionising.
Stopped by = thick concrete or a few cm's of lead.
Uses of Radiation l
Alpha - Ionisation is useful for smoke detectors.�Smoke detectors have a weak source of�A radiation close to two electrodes. The radiation ionises the air and acurrent flows between the electrodes. If theres a fire, the smoke absorbs the radiation and the current stops.
Beta radiation�= tracers and monitoring the thickness of materials.
Doctors may use radioactive chemicals called tracers for medical imaging. Certain chemicals concentrate in different damaged or diseased parts of the body, and the radiation concentrates with it. Radiation detectors placed outside the body detect the radiation emitted and build up an image of the inside of the body.
Radiation is used in industry in detectors that monitor and control the thickness of materials such as paper, plastic and aluminium. The thicker the material, the more radiation is absorbed and the less radiation reaches the detector. It then sends signals to the equipment that adjusts the thickness of the material.�
Uses of Radiation ll
Gamma radiation is used in the treatment of cancer, testing equipment and sterilising medical instruments.
They are used to sterilise equipment because they kill microbes.
Gamma can also be used for non-destructive testing.
The radiation can be used to detect cracks or faults in machinery.
Gamma radiation can also be directed at cancerous cells in the body. This must be directed carefully to ensure that not too many other body cells are damaged.
planets reflect sunlight and orbit the sun in ellpises.
Inner planets - Mercury, Venus, Earth, Mars
Outer Planets -Jupiter, Saturn, Uranus, Neptune.
Differences between planets and stars
Planets = reflect sunlight, smaller, nearer, have moons
Stars = Emit light, huge, further away
Things only change direction when a force acts upon it.
Bigger the object - more gravitational pull it has
Further away the object�- weaer its gravitational pull.
Gravity keeps comets, asteroids, satellites and moons in orbit.
Gravity�makes objects that are already moving (Earth) change their course like into�circular or elliptical orbits.
Circular motion is alwasy caused by a force (often gravity) towards the�centre of a circle.
A force that causes circular motion is called a centripetal force.
Asteroids & Comets
Theres a belt of asteroids orbiting between Mars and Jupiter.
When the solar system was forming, these asteroids didnt form a planet because Jupiters gravitational force kept interfering.
Asteroids are piles of rock and rubble, sometimes the pull from other planets forces the asteroids to be pushed or pulled elsewhere
Comets orbit the sun in very elliptical orbits. They are balls of ice, dust and rock which orbit the sun in elongated ellipses.
They come from objects orbiting the sun way beyond the planets. As the comet approahes the sun, the ice melts leaving the tail of gaseous materials and debris which can be millions of miles long.
Comets speed up as they come closer to the sun due to the gravitational pull.
meteorties = rocks that have crashed down to Earth.
the atmosphere usually burns up any meteroites on entry, but if they are big enough they can fall too earth.
They can cause climate change due to the amount of dust and smoke that is kicked up on impact. It can block out sunlight and cause species to become extinct.
E.g. 65 million years ago, a meterotite hit the Yucatan peninsula in Mexico. It was around 10km in diameter and caused climate change. (Could be the cause of the dinosaurs to become extinct)
Evidence for meteroites: Craters, unusual elements in rock layers, change in fossil numbers due to extinction.
Galaxies, light years and black holes.
Our sun is one of millions in the Milky Way galaxy. (one of the spiral arms) The whole universe has over one billion galaxies.
Galaxies are very far apart from eachother. The universe = mostly empty space.
Scientists measure distance in space in light years.
A light year = the distance that light travels through a vacuum over the period of a year. A light year is a unit of distance NOT TIME.
When a star has used up all of its energy, it explodes. This explosion levas an extremely dense material, it's so dense that nothing can escape its gravitational attraction. This is called a Black hole.
Black hole = large mass, small volume & high density.
Black holes arent visible, because even light gets pulled in by it's gravity. Astronomers have to detect them in other ways like; observing x-rays emitted by hot gases from other stars that have been pulled into the black hole. �
The solar system is huge. It takes radio waves several hours to cross it.
Sending manned spacecraft would take a few years.
The spacecraft would be very expensive, heavy and would require a lot of fuel.
Making it suitable to sustain life
-Food, water, oxygem
-regulate temperaturess and remove toxic gases from the air
-shielded from radiation
-long periods in a low gravity environment canl ead to muscle wastage and loss of bone tissue
Fly-by missions - Simplest. It doesnt land, it flies by and collects data like temp. radiation levels and magnetic and gravitational fields.
Other probes are designed to land, and then urn up after sending the collected data back to earth.
Some probes are designed to land and wander around with the ability to take pictures.
Advantages - no water, food or oxygen needed, can with stand lethal conditions, lighter, less is spent on safety measures, no-one potentially gets hurt.
Disadvantages - Can't think for themselves, if something goes wrong little can be done, cant do maintenance on itself.
Information collected - Distant objects - data needs to be beamed back by radio waves etc. nearer objects - samples and information can be physically brought back.
Origins of the universe
The universe is expanding, galaxies are moving further apart.When we look at light from distant galaxies, the frequencies are lower. They're shifted to the red end of the spectrum.��The further away you are from it, the smaller the frequency.
Measurements of the red-shift suggests that all of th distant galaxies are moving away from us.
More distant galaxies habe greater red-shifts than the nearer ones.
This means that the more distant galaxies are moving away faster tthan nearer ones.
Scientists can detect low frequency microwave radiation that comes from all directions of the universe. This is known as cosmic background radiation.
This background radiation is strong evidence for The Big Bang Theory. As the universe expands and cools, this background radiation also 'cools' and drops in frequency.
The Big Bang Theory
1)At the start, all of the matter occupied a very small space, in space.
�The matter occupied an area�much much smaller than�the size of a pin head.
�Then it exploded and expanded.
�Expansion is still going on today.
2)The Big Bang Theory allows us to estimate the age of the universe according to the rate of expansion.
We think the universe is around 14 billion years old.
3) This isnt exact because we don't know whether expansion has sped up or slowed down since the Big Bang.
near aerth objects are asteroids or comets that maybe on a collision course with Earth.
Telescopes and satellites are used to search and track the trajectory of the NEO.
Small NEO's would burn up on entry, but larger ones could cause powerful explosions.
To deflect it you can explode a bomb to nudge it into a different path and orbit.
The moon is believed to be the product of a side on collision between another planet and Earth.
In the heat of this collision, the two dense iron cores merged to give the core we have today.
The less dense material was ejected as rocks and dust that orbited earth. These then clumped together to from the moon.
Evidence; the moon has a lower density than the Earth and does not have an iron core.
Moon rocks contain few materials that evaporate at low materials suggesting that the moon was formed from hot material.
Uses uranium as fuel.
In nuclear fission, the nuclei of the atoms in the fuel are split in two, this releases a lot of energy.
Water is used as a coolant. This produces steam which drives a turbine in the generator.
Advantages; lots of energy produced and little carbon dioxide is emitted. Nuclear fuel is relatively cheap. There's still lots of uranium left.
Disadvantages; nuclear power stations are expensive to build and maintain. Radioactive waste is very hard to dispose of or reprocess. Processing the uranium making it safe to use is expensive.
Nuclear bombs and safety measures
After reprocessing uranium, you're left with more uranium and a bit of plutonium. The uranium can be reused in the power station, but the plutonium can be used to make nuclear weapons.
You should keep radioactive material in a labelled, lead-lined box. Exposure time should be at a minimum. Never allow skin contact. Keep it at arms length. Avoid looking directly at it.
If you work with radioactive materials; full protective suits. Lead screens, suits and barriers. Robotic arms to handle highly radioactive material.
Disposing of radioactive waste
Low level radioactive waste can be disposed of by burying it in secure landfill sites.
High level waste can stay radioactive for thousands of years and is often sealed in glass blocks which are then sealed in metal canisters. This allows them to be buried deep underground. These places must be geologically stable.
After a place is found, most people living there object so most waste is kept on site at the moment.
Waste can be reprocessed, but even this leaves waste behind.
There are strict regulations about disposing of radioactive waste, but these could change In The future as our knowledge of radioactive materials increases.
Power stations are at risk of terrorist attacks.
The life cycle of a star
Stars form from clouds of gas and dust called a NEBULA.
The force of gravity forces the nebula o spiral together and form a PROTOSTAR.
Gravitational energy is converted into heat energy, so the temperature rises.
When the heat energy rises, hydrogen nuclei undergo thermonuclear fusion which produces helium nuclei. This helium gives out huge amounts of heat and light energy. This is the stars stable period and the heat created provides outward pressure which balances the force of gravity that pulls everything inwards. This is a MAIN SEQUENCE STAR.
Eventually, the hydrogen begins to run out and it swells into a RED GIANT as the surface cools.
Small stars and Big stars
Small stars; After going through its red giant phase, the star becomes unstable and ejects an outer layer of planetary dust and gas. This forms a PLANETARY NEBULA.
This leaves behind a small and very dense core called a WHITE DWARF which will cool and eventually fade away.
Big stars; after the red giant phase, big stars form red supergiants. The bright glow will return as the star undergoes more fusion. The star will expand and contract several times and produce heavier elements in various nuclear reactions. This will lead to an explosion called a SUPERNOVA.
The exploding supernovae ejects its outer layer of dust and gas to leave a very dense core. This is a NEUTRON STAR.
if the star is big enough, it will become a BLACK HOLE.