2.1 Waves Flashcards
Name and give an example of the 3 types of waves
Transverse - EM waves
Longitudinal - Sound waves
Mechanical - Seismic waves
Give 2 similarites and differences between transverse and longitudinal waves
Transverse: Oscillate perpendicular to the direction of travel Can be polarised Longitudinal: Oscillate parallel to the direction of travel Has to move through a substance Both: Transfer energy Interfere with other waves
Define polarised light
Light that has passed through a polarising filter which has limited the light to one plane of vibration
Describe how the amount light passing through 2 polarising filters, initially parallel, changes as the second filter is rotated 180°
The amount of light will be maximun at 0°. When the filter is rotated to 90° the amount of light passing through the filters will decrease until at 90° no light will pass through. As the filter is rotated to 180° the amount of light will increase again until there is another maximun at 180°
Define the amplitude of a wave
The maximum displacement a vibrating particle reaches from the position of equilibrium
Define the wavelength of a wave
The distance between the same point on successive waves e.g crest to crest
Define the period of a wave
The time taken for a complete wave to pass a fixed point
Define the frequency of a wave
The number of complete waves that pass a stationary point in a second
What is the phase difference of 2 particles half a wavelength apart?
π or 180°
What is the phase difference of 2 particles a quarter of a wavelength apart?
½π or 90°
What is the phase difference of 2 particles a full wavelength apart?
2π or 0/360°
What are the 3 processes that can occur to waves?
They can be reflected, refracted or diffracted
When does maximum diffraction occur?
When the gap is the same size as the wavelength of the wave
What are the 2 types of interference and when do they occur?
Constructive interference occurs when 2 waves in phase meet and their amplitude adds to form a greater amplitude
Destructive interference occurs when 2 waves which are out of phase meet and their amplitude cancel each other out
When is a stationary formed?
When a wave is reflected at its source forming 2 waves travelling in opposite directions with the same frequency
When does the first harmonic occur?
When there is one antinode
In wave equations what does L represent and what is it measured in?
The length of string and is measured in metres
Define coherent souces
When 2 sources of waves have the same frequency and a constant phase difference
What does T represent in wave equations and what is it measured in?
Tension measured in Newtons
What does µ represent in wave equations and what is it measured in?
Mass per unit length measured in kg/m
How do particles in a stationary wave vibrate?
They vibrate with the same frequency except those at nodes where there is no vibration
At what amplitude to particles in a stationary wave vibrate?
The amplitude varies from zero at nodes to maximum on antinodes
