P6 - Waves Flashcards
What is the definition of frequency?
Number of complete waves passing a certain point each second.
What is the period?
The amount of times it takes for a complete wave to pass a point.
What is the amplitude?
Maximum displacement of a point on a wave from its rest position.
What is the wavelength?
The length of a full cycle of a wave
What is a transverse wave?
Oscillations perpendicular to direction of energy transfer.
What are 3 examples of a transverse wave?
- Ripples in water
- Electromagnetic waves (eg. Light)
- Waves on a string
What is a longitudinal wave?
Oscillations parallel to direction of energy transfer.
What are 2 examples of longitudinal waves?
- Sound waves
- P - waves
What is refraction?
When a wave changes direction as it crosses a boundary between two materials at angle to the normal.
What 3 things are EM waves?
- Transverse
- Transfer energy from source to absorber
- Travel at some speed in air or vacuum.
What are the EM waves in order?
Radio waves
Microwaves
Infrared
Visible light
Ultra violet
X - Rays
Gamma Rays
What are radio waves used for?
TV
Radio
What are microwaves used for?
Satellite communications
Cooking
What are infrared waves used for?
Electric heaters
Cooking
Infrared cameras
What are visible light used for?
Communications through optical fibres
What is UV used for?
Energy sufficient lights
Sun tan beds
What are X - Rays and gamma rays used for?
Medical imaging
Medical treatments
How can UV be dangerous?
Can prematurely age skin
Increases risk of skin cancer
How can X - Rays and gamma rays be dangerous?
Gene mutation
Cancer
How can X - Rays and gamma rays be dangerous?
Gene mutation
Cancer
What does the earth do in daytime?
Absorbs more radiation than it emits
What does the earth do in nighttime?
Earth emits more radiation than it absorbs.
What does the earth do in nighttime?
Earth emits more radiation than it absorbs.
How does sound travel through air?
As a series of compressions and rare fractions
What does the sound hitting a solid cause to happen?
Particles in the solid to vibrate
Particles hit next particles in line and so on
How do sound waves travel through a solid?
As series of vibrations
What happens when a compass isn’t near a magnet?
It’s needle points north to line up with the earths magnetic field.
What are two factors that the magnetic field strength depends on?
Size of current
Distance from the wire
What does twisting a wire into a solenoid do?
Increases the magnetic field strength around the wire
What is an electromagnet?
A solenoid with an iron core. It is a magnet that can be turned on and off.
What are 3 ways to increase force?
Increase the current
Increase the magnetic field strength
Increase the length of the conductor
What are three ways to increase the force?
Increase the current
Increase the magnetic field strength
Increase the length of the conductor
What are electric motors?
Direct current is passed through wire
Each side of the coil experiences opposite forces
Coil rotates
What are alternators?
Generate alternating current
What are dynamos?
Generate direct current
What is a step up transformer?
Increase the voltage from the primary coil to the secondary coil
What is a step down transformer?
Decreases voltage from primary coil to the secondary coil.
What is a permanent magnet?
Produces its own magnetic field
Where is magnetic field strongest?
At the poles
When does the magnetic field strength decrease?
With distance from magnet
What do field lines show?
Direction force would act on a North Pole, if placed at the point.
What are the four magnetic materials?
Iron
Steel
Nickel
Cobalt
