What does a wave do?
Transfers energy with no need for overall transfer of matter
What is the frequency?
Number of vibrations per second. Measured in Hertz, kilohertz, megahertz, or gigahertz
What is the wavelength?
Distance from one peak/trough to another. Measured in cm/m
What is the amplitude?
Ance from equilibrium to peak/trough. Measured in m/cm
What is the wave speed?
Wave speed(m/s) = frequency(Hz) x wavelength(m)
What should you do for maximum diffraction?
Have the size of the gap or obstacle roughly the same size as the wavelength
Will longer or shorter wavelengths diffract more?
Longer
What is a transverse wave?
When transfer of energy is perpendicular to disturbance of particles
What is a longitudinal wave?
When energy moves in the same direction to disturbance of particles.
What are the areas in a longitudinal wave?
Rare fraction- low pressure
Compression- high pressure
What are the parts of the electromagnetic spectrum? (Raging martians invaded venus using x-ray guns)
In increasing energy + frequency, but decreasing wavelength: Radio Microwave Infrared Visible spectrum Ultraviolet X-ray Gamma
What are radio waves used for?
Used to transmit radio and TV programs. Not know if harmful
What are microwaves used for?
- used in microwave ovens, as freq. of waves matches natural vibrations of food molecules, so they vibrate, increasing the temperature and cooking the food
- some used in satellite communications, as can pass through atmosphere easily
- they can harm us, as we are mainly water, so it burns/damages/kills cells
What are infrared waves used for?
- everything emits it as it is just vibrating atoms
- used to cook food, ie. in toasters
- use in TV remotes
- as infrared is just heat, it can burn us when concentrated
What are visible spectrum waves used for?
- this is light we can see ∴ photography and books
* can damage eyes if you look at it for long enough, by burning spot on your retinas
What are ultraviolet waves used for?
- used in security inks and paints, as can only be seen under UV
- used in tanning beds
- can lead to cells mutating. Causes damage to surface cells and blindness. People with darker skin less likely to gte skin cancer than fairer people, as their skin absorbs UV better
What are x-ray waves used for?
- to scan bones. The x-rays penetrate skin and muscle but not bones leaving a shadow picture
- also used to check metal for cracks/damage in industry
- can cause cancer if they interact with your DNA
What are Gamma rays used for?
- sterilise medical instruments by killing bacteria
- kill cancerous cells in radiotherapy
- cause cancer by damaging cells and DNA, as short wavelengths with high energy can easily penetrate tissue. V dangerous
What is the difference between analogue and digital signals?
- analogue can have any amplitude and frequency
* digital is only in two states- on or off
Why do we need to amplify signals?
- as a signal travels it becomes attenuated- the amplitude decreases
- be need to amplify the amplitude using repeaters
- this amplifies noise and signal
Why is digital better than analogue?
- with analogue, you can’t know what the value of the signal was before noise, as it could be anything, and noise is random
- although digital signals still pick up noise, they can be regenerated perfectly, as they only have 2 values
- easier to reduce noise
- maintain quality over longer distances
- digital carries more info per sec
When do magnets attract and repel?
North repels north, and vice versa.
South attracts north, and vice versa.
What materials are magnetic?
Cobalt, iron, nickel, steel. You can test this by placing a magnet in a tray of iron filings
Describe the magnetic field around one bar
The field is strongest around the poles, so the iron filing will crowd around there
