C11-12. Waves Flashcards
Define a progressive wave.
This is a wave that transfers energy, causing the particles of the medium it travels through to oscillate about a fixed position.
What is a transverse wave?
A wave in which particles oscillate perpendicular to the direction of wave propagation.
What is a longitudinal wave?
A wave in which particles oscillate in parallel to the direction of wave propagation.
What is displacement?
The distance of a point on a wave from its equilibrium position.
What is amplitude?
The maximum displacement of a particle from its rest position.
What is wavelength?
The minimum distance between adjacent points oscillating in phase on a wave.
What is time period?
The time taken for one full wave cycle to be completed.
What is frequency?
The number of complete cycles passing a point per unit time.
How do we define phase difference?
The difference in displacements of particles along a wave.
What units are usually used for phase difference?
Degrees or radians, or metres.
What do we mean if we say two particles are in-phase?
Both particles reach their maximum displacement at the same time - they oscillate in-step.
What do we mean if we say two particles are in antiphase?
Both particles oscillate completely out of step, so as one reaches its maximum positive displacement, the other reaches its max. minimum displacement.
What is the phase difference between two particles in-phase generally?
Either 0 or an even integer coefficient of pi radians.
What is the phase difference between two particles oscillating in anti phase generally?
An odd integer coefficient of pi radians.
What equation links frequency, wavelength and wave speed?
v=f*lambda
Define reflection.
When a waves changes direction at a boundary between two media, remaining in the original medium.
State the law of reflection.
When 2 waves are reflected, the angle of incidence is always equal to the angle of reflection.
Define refraction.
When a wave changes direction as it passes through one medium into another.
If a light wave enters a more dense medium, what can we say about its new speed and direction?
It will travel more slowly, and its angle of refraction will be closer to the normal line.
If a light wave enters a less dense medium, what can be said about its new speed and direction?
It will travel more quickly, and its angle of refraction will be further from the normal line.
Why doesn’t reflection affect wavelength?
Reflection does not impact wave speed or frequency, so has no impact on wavelength.
How is wavelength affected by entering a denser medium?
Wavelength decreases, and frequency remains unchanged.
Define diffraction.
The process in which a wave spreads out when it passes through an aperture.
This effect is most prominent when the slit/gap is around the same size as the wavelength.
When does total internal reflection occur?
This occurs when the angle of incidence is such that the angle of refraction becomes 90 degrees.
This angle of incidence is then called the critical angle.