What does light do?
It transfers energy from the source to our eyes. Light is a type of electromagnetic wave.
The electromagnetic spectrum
- Gamma ray
- X ray
- Ultraviolet
- Visible light
- Infrared
- Microwave
- Radio wave
Gamma rays function
Used for sterilising medical equipment and food and detection and treatment of some cancers.
X ray function
Used for medical imaging and airport security scanners.
Ultraviolet function
Used for sterilising water and killing bacteria. Also used to detect forged bank notes.
Visible light functions
Used for lighting, photography and fibre optic communications.
Infrared functions
Used for short range communications, e.g. tv remotes. Also for electrical heaters, cooking food, optical fibres and thermal imaging cameras.
Microwave functions
Used for satellite communications and cooking food.
Radio wave functions
Used for radio and tv broadcasting and satellite communications.
The PEN table
Used to work out the mass, charge and location of the proton, electron and neutron.
Electrons discovery
Plum pudding model 1904 (Thompson)
Nucleus discovery
In the centre/positive charge 1913 (Rutherford)
What did Chadwick do?
He demonstrated the presence of neutrons.
What did Bohr do?
He discovered the electron shells have set energy levels (2.8.8).
What are some commons sources of large amounts of background radiation?
- Bananas
- Some rocks
- Radiation from space
How do Geiger Muller tubes work?
GM tubes are connected to a counter that show the number of ions/ionised particles per minute.
What are the types of radiation?
- Alpha
- Beta
- Gamma
Properties of alpha radiation?
- 2 protons plus 2 neutrons (the nucleus of helium)
- stopped by paper
- heaviest relative mass
- positive
- can travel 5 cm before stopping
- very strongly ionising.
Properties of beta radiation?
- Lighter electron mass (1/1835)
- Negative
- Travels 15 cm before stopping
- Stopped by a few mm of aluminium
- Strongly ionising
- 1 electron
Properties of gamma radiation?
- Penetrates furthest
- Can travel several metres
- It is not a particle (no mass, no charge)
- It is a wave (pure energy)
- It is stopped by a few cm of lead only
- Weakly ionising.
Positron
The anti-particle to the electron.
* beta radiation can also produce particles with the same mass of an electron but positively charged.
What are the 8 energy stores?
- kinetic
- gravitational potential
- thermal
- chemical
- nuclear
- elastic
- magnetic
- electrostatic
What are the 4 energy transfers?
- forces
- electricity = the movement of charges (electrons/ions)
- heating
- radiation
When does induced electrostatic charge appear?
When a charged object causes the movement of charges in another object (without touching it).
