The solar system contains…
Planets Dwarf Planets Moons Artificial satellites Asteroids Comets
Planets…
Large objects that orbit a star
Dwarf planets…
These are planet-like objects that aren’t big enough to be planets
Eg. Pluto
Moons…
These orbit planets with almost circular orbits
They are a type of natural satellite (not man made)
Artificial satellites…
Ones humans have built that usually orbit the Earth in a fairly circular orbits
Asteroids…
Lumps of rock and metals that orbit the Sun
Usually found in the asteroid belt
Comets…
Lumps of ice and dust that orbit the Sun
Orbit usually highly elliptical- a very stretched out circle
Some travel from near the Sun to the outskirts of our Solar system
Planets in our solar systems…
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune (Pluto)
Objects in a circular orbit at a constant speed is…
Constantly accelerating
The force which causes circular orbit is…
Centripetal force
It acts towards the centre of the circle
The centripetal force cause the object…
To just fall towards whatever it’s orbiting
But as the object is already moving, it causes it to change direction
The object keeps accelerating towards what its orbiting but the … (which is at a right angle to the acceleration)…
Instantaneous velocity
Which keeps it travelling in a circle
The force that makes the orbit travel in a circle is provided by…
Gravitational force between the planet and the Sun
Gravitational field strength depends on…
The larger the…
Body creating the field
Mass of the body, the stronger it’s gravitational field
Gravitational field also varies with…
With distance
The closer you get to a star or planet, the stronger the gravitational force is
The … the force, the … the instantaneous velocity needed to … it
Therefore the closer to a star or planet you get, the…
Stronger/Larger/Balance
The faster you need to go to remain in orbit
For an object in a stable orbit, if the speed of the object changes , the size of the its orbit…
Faster moving objects will move in a stable orbit with…
Must do too
A smaller radius than slower moving ones
Geocentric model…
The Sun, moon and planets and stars all orbit Earth is perfect circles
Accepted model during the Ancient Greeks times until 1500s
Heliocentric model…
Earth and all of the planets orbited the Sun in perfect circles
Galileo evidence- Jupiter’s moons
The modern model…
Planets orbit the Sun
But in elliptical orbits
Steady state theory…
No beginning or end (has existed and always will)
As the universe expands, new matter is constantly being created
This means that the density of the universe is always roughly the same
The Big Bang theory…
The tiny space was very dense and very hot
Explosion - the space starts expanding and still does
Finite age
Currently the accepted theory
Evidence for the Big Bang theory
Red shift- wavelengths and frequency of the light spectrum change and move more towards the red
Cosmic Microwave Background Radiation- remains of the energy created from the Big Bang theory
Expanding- this supports the theory of a single explosion
Lifecycle of a star…
Nebula, Prostar, Main sequence star, Red supergiant (/Red giant) Supernova (/White dwarf) Neutron star or black hole
Nebula…
Cloud of dust and gas
Prostar
Force of gravity pulls dust and gas together
Temperature rises as the star gets denser
More particles collide with each other
Hydrogen nucleus can undergo nuclear fusion to form a helium nuclei
Lots of energy = hot
Main sequence star
Long stable period
Outward pressure of thermal expansion balances the force of gravity pulling everything inwards
Lasts billions of years
Red giant/supergiants
The hydrogen in the core runs out Gravity force is larger than pressure, compressing the star until it is hot and dense enough to make the outer layers expand Becomes red because the surface cools Red giant- small star Red supergiant- larger star
White dwarf
Small- medium star ejects it’s outer layer of dust and gas
Leaving behind a hot, dense solid core
Supernovas
Start to undergo fusion again
Expand and contract serval times as the balance shifts between gravity and thermal expansion
Explode in a supernova
Neutron star
A very dense core left from the exploding supernova when the outer layers of gas and dust are thrown into space
Black hole
If the star is big enough it will collapse
Forming a black hole, a very very very dense point in space
Light can’t escape from it
How to improve the quality of an image on a telescope
Increase the aperture
Use a higher quality objective lens
What can effect the image from a telescope
The atmosphere (absorbs light) Pollution - light and air pollution from the cities
Best view for a telescope
On top of a mountain because…
- Less atmosphere above it
- In a dark place away from cities
(Or in space to avoid the atmosphere all together)
X rays telescopes
Can see violent, high temperature events in space, like exploding stars
Radio telescopes
Responsible for the discovery of the cosmic microwave radiation, learnt more about origin of the Universe
Modern telescope
Better resolution
Gather more light
Improved magnification
Work alongside computers
EM radiation in (to an electron)
electron absorbs the energy
gets ‘excited’
moves up to the next electron shell-energy level
further away
EM radiation out (of an electron)
electron falls back down to lower energy level
excess energy carried away by EM radiation
closer together
transmit energy
What happens to an atom if it looses an electron
atoms can become ionised
if enough energy has been absorbed the outer electron could leave the atom
=positive ion
Alpha particles splurge
helium nuclei don't penetrate far into materials - can only travel a few cms in air and are absorbed by thin paper random come from nucleus of an unstable atom strongly ionising
Beta particles splurge
fast moving electrons or positrons
moderately ionising
have a range in air of a few metres and absorbed by a sheet of aluminium
positrons can produce gamma rays when they hit an electrons
Gamma rays splurge
NOT A PARTICLE
EM waves with a short wavelength
after nucleus is decayed gamma rays are released to carry away the energy
penetrate far into materials
weakly ionising
can be absorbed by lead or metres of concrete
What measures radioactivity
Geiger- Muller tube
Photographic film
Half life definition
is the average time taken for the number of radioactive nuclei in an isotope to halve
Background radiation sources
naturally occurring unstable isotopes- in the air, some foods, building materials and some rocks
radiation from space- cosmic rays (our atmosphere protects us from most of it)
radiation due to human activity- fallout from nuclear explosions or nuclear waste (tin proportion)
Exposure to radiation
CALLED IRRADIATION
objects near radioactive sores get irradiated which means they are exposed to it
sources can be placed in lead boxes or standing behind barriers or being in a different room can reduce irradiation
Radioactive particles getting onto objects
CALLED CONTAMINATION
unwanted radioactive atoms getting onto an object
the contaminating atoms may decay which releases radiation causing harm
contamination is dangerous if inside your body
gloves tongs and protective suits are used in order to reduce contamination
Radiation damages cells by…
IONISATION
can cause tissue damage
low dosage = minor damage = give rise to mutant cells = divide uncontrollably = cancer
high dosage = kills cell completely = radiation sickness
Beta and gamma most dangerous outside the body because they can penetrate the skin and damage delicate organs (alpha cant penetrate the skin)
Alpha most dangerous inside the body, strongly ionising
Alpha radiation use
Household fire alarms
weak alpha radiation placed in smoke detector, next to two electrodes
source causes ionisation and a current flow
fire = smoke absorbs radiation = current stops and the alarm sounds
Gamma rays use
food can be irradiated by high dosages of gamma rays which will kill all microbes
medical equipment can be sterilised similarly with high dosage of gamma rays
doesn’t require high temperatures therefore there is no damage
radioactive source needs a long half life = doesn’t need replacing for months
Beta radiation use
thickness control
direct radiation through the stuff being made (eg. paper), with detector the other side connected to a control unit
when the amount of detected radiation changes the thickness is too thin or thick, so control unit adjusts the rollers to give correct thickness
Beta and gamma use
Tracers
Medical tracers can be used to detect and diagnose patients with medical conditions using an external detector
MUST BE BETA OR GAMMA EMITTERS so that radiation passes out of the body without doing too much damage
should have a short half life so that radioactivity in a patient disappears quickly
Gamma emitting tracers can detect leaks in underground pipes
PET scanning and radiotherapy
on written flashcards
Nuclear fission - what is it
releases energy from uranium (or plutonium)
chain reactions
nuclear fission - process
slow moving neutron is fired at a large unstable nucleus (eg. uranium-235)
neutron absorbed by the nucleus making the atom more unstable and causes it to split
forms two lighter daughter elements (eg. barium or krypton)
also forms two or three neutrons
How to control the chain reactions
fuel rods - slow down the fast moving neutrons
control rods- often made of boron limit the rate of fission by absorbing excess neutrons, they are lowered and raised to control the chain reaction
Nuclear power stations
powered by nuclear reactors - controlled chain reactions created
energy released transferred to kinetic energy (after the process in the reactor) of a turbine, then to generator where the energy is transferred away from the generator electrically
Nuclear fusion - what is it
two light nuclei collide at high speed and fuse to create a larger and heavier nucleus
eg. hydrogen nuclei can fuse to produce a helium nucleus
energy is also released as radiation
fusion - conditions and difficulties
can only occur at very high temperatures and pressures
this is because the positively charged nuclei have to get very close in order to fuse
so a strong force is needed to overcome the electrostatic repulsion
conditions are hard and expensive to try and build
Advantages of nuclear power
it generates huge amounts of energy from a relatively small amount of nuclear material (which is cheap and readily available)
Don’t release any greenhouse gases, so therefore a clean source of energy
Reliable energy source therefore we don’t need to use as many fossil fuels
relatively safe way of producing electricity
Disadvantages of nuclear power
Cant be disposed of safely because very long half lives (radioactive for years), also if there is a leak they can pollute land, rivers and streams.
may be seen as dangerous- public perception
carries risk of leaks and major catastrophes eg. Chernobyl and Fukushima
expensive to build and decommission