(3.1) - Progressive and Stationary Waves Flashcards
Amplitude
The maximum displacement of a wave from its equilibrium
Frequency
The number of complete wave cycles that pass a given point in one second
Wavelength
The distance between two consecutive points that are in phase on a wave
Speed
The rate at which a wave travels through a medium
Phase
The position of a point within one complete cycle of a wave
In phase, Out of phase, Anti phase
Phase difference in Stationary wave
- In phase: every particle between 2 nodes (including antinode)
*
Stationary wave phase difference rule:
- If particles are seperated by an odd number of nodes, they are pi out of phase (180 degrees)
- If particles are seperated by an even number of nodes, they are in phase (0 degrees)
Definition, properties, and examples
Longitudinal Waves
- Oscillates parallel to direction of wave travel
- Compressions and rarefractions
- Sound waves, seismic P
Definition, properties, and examples
Transverse Waves
- Oscillates perpendicular to the direction of wave travel
- Oscillates in crests and troughs
- Waves on a string, seismic S
Polarised wave
Wave which only oscillates in one plane
Why can’t longitudinal waves be polarised
They only oscillate parallel to direction of travel
Uses of polarisation
- TV and radio signals
- Sunglasses
How they work, and examples:
Polarisation in Alignment of Aerials for Transmission and Reception
- Transmitted waves from towers are recieved from antenna. Antenna must be alligned with polarised waves from tower for max strength
- Tv and Radio
What is a stationary wave?
Two waves with same frequency and amplitude travel in opposite directions and superpose with each other
What is a node?
Region on stationary wave with no vibrations
What is an antinode?
Region on stationary wave where vibrations are at maximum amplitude
Superposition
The displacements of two waves are combined as they pass each other, and the resultant displacement is the vector sum of each wave’s displacement
‘In phase’
Two waves that both:
* have the same frequency
* are at the same point in their cycles at the same time
‘Anti-phase’
Two waves that both:
* Have the same frequency
* Have a phase difference of 180 degrees
‘Out of phase’
Two waves that:
* Can have the same of different frequencies
* Can have any phases difference, except 0, and any multiple of 180 degrees
Constructive interference
2 waves with same frequency and amplitude are in phase, and their amplitudes combine
Destructive interference
2 waves with same frequency and amplitude are anti-phase, and their amplitudes combine
How does a stationary wave on a string form?
- Wave reflects off fixed end and superimposes with itself.
- First harmonic has 2 nodes and 1 anti-node
How does a stationary wave using a microwave form?
- A microwave source reflects off a metal plate, and forms a stationary wave.
- Microwave probe can detect nodes and anti-nodes
How does a stationary wave in sound waves form?
- Using a loudspeaker inside a closed column creates sound waves.
- This can be demonstrated by placing fine powder inside the column; at certain frequencies, it gathers at nodes, showing zero disturbance.
Phase difference = Path difference equation
Δϕ = 2πd / λ
