Waves Flashcards
What is a progressive wave?
A wave that transfers energy from one place to another without transferring any matter. The transfer of energy is in the same direction as the wave is travelling.
State four ways you can demonstrate a progressive wave transfers energy.
EM waves cause things to heat up which transfers energy.
X-rays and gamma rays knock electrons out of their orbits, causing ionisation.
Loud sounds cause large oscillations in air particles which can make them vibrate.
Wave power can be used to generate electricity as waves can carry energy.
Define wavelength
The distance between two identical points on a wave.
Define amplitude.
The maximum displacement of a wave from its equilibrium position.
Define period.
The time taken for a wave to complete one full cycle.
Define frequency
The number of complete oscillations of a wave per second.
What is the wave speed equation in symbols?
v = f x λ
How is time period linked to frequency?
f = 1/T
What is a transverse wave?
A wave whose oscillations are perpendicular to the direction of energy transfer.
What is a longitudinal wave?
A wave whose oscillations are parallel to the direction of energy transfer.
Describe a longitudinal wave in terms of pressure variation and the displacement of molecules.
Longitudinal waves in a fluid consists of areas of compression and rarefaction. These compressions and rarefactions creature variations in pressure in the medium.
Areas of high pressure (compression) are where molecules in the medium are close together.
Areas of low pressure (rarefaction) are where molecules in the medium are far apart.
Areas of rarefaction move into vacant spaces creating vacant spaces behind them. Areas of compression push neighbouring particles into vacant spaces. This allows the movement of the wave.
What is a wavefront?
A line joining all points in a wave that are in phase and are drawn perpendicular to the direction of wave travel.
What is a standing wave?
A wave that stores energy at the nodes and antinodes instead of transferring it.
What conditions are needed to produce a stationary wave?
Two progressive waves must be travelling in opposite directions in the same medium, in the same plane.
The waves must be coherent; same frequency, same wavelength.
The two waves superpose together.
What is a node?
It is a point at which the displacement in a standing wave is at its minimum due to the wave being in antiphase, causing total destructive interference.
What is an antinode?
It is a point at which the displacement in a standing wave is at its maximum due to the wave being in phase, causing constructive interference.
Define superposition.
When the total displacement of a wave at any point is equal to the vector sum of the individual displacements.
Define coherence
Same type of waves that have same wavelength, same frequency and fixed phase difference.
Define interference
The pattern observed when two or more waves superpose with each other (could be the pattern of light, sound, microwaves etc).
What is the fundamental frequency equation in symbols?
v/2L or (√ (T/μ))/2L
What factors affect the speed of a wave on a string?
Tension.
Mass per unit length.
What is meant by the intensity of wave?
The power transferred by a wave per unit area.
What is the relationship between intensity and amplitude of a wave?
I α A^2
What is the equation for the intensity of a wave?
I = P/A