3: Waves Flashcards
What is the frequency of a wave?
How many waves there are per second.
Where can you find the amplitude on a wave?
From the equilibrium position to the crest of a wave.
What is wavelength?
It describes the same point in a cycle.
What are progressive waves?
Waves which transfer energy from one place to another. However, the particles within the wave do NOT move.
What is the time period of a wave?
The time taken for 1 complete oscillation.
What are circular wave fronts?
Waves which come from a point source, they propagate radially and in 3D they would form spheres.
What is the wave speed equation?
wave speed = wavelength / time period
What is the frequency equation?
Frequency = 1 / time period
What is the speed of light?
3 x 10^8 m/s OR ms^-1
What is phase difference?
It can be described using wavelength. We measure what phase a point is on in degrees.
What is the equation for phase difference?
phase difference = phase a - phase b
What is the idea of radians?
A full circle can be split into radians.
90 degrees - Pi/ 2 rad
180 degrees - Pi rad
270 degrees - 3 x Pi / 2 rad
360 degrees - 2 Pi rad
What are the equations for arc length?
(Pi x diameter) x angle given / 360
radius x angle given
What is it called when particles are half a wavelength out of phase?
Antiphase.
What is it called when particles are a whole wavelength out of phase?
in phase.
What are transverse waves?
When particles oscillate perpendicular to the direction of energy transfer. E.g. water waves.
What are longitudinal waves?
When particles oscillate parallel to the direction of energy transfer. They contain compressions and rarefactions. E.g. sound waves.
What is polarisation?
A feature of transverse waves only. A wave is plane polarised if all vibrations in the wave are in a single plane, which is perpendicular to the direction of propagation of the wave.
What are standing waves?
Where waves appear to be still.
How are standing waves formed?
When two coherent progressive waves are superposed. They must be:
- equal frequency
- nearly or the same amplitude
- same speed
- travelling in opposite directions
What are nodes?
Points at which no displacement occurs.
What are antinodes?
Points at which maximum displacement occurs.
What is interference?
When two waves interact with each other.
What is superposition?
The resultant wave due to the interference.
When do waves interfere?
When they are in the same medium.
What is constructive interference?
When waves in phase interfere with each other.
What is destructive interference?
When waves are in antiphase and interfere with one another.
When can standing waves exist?
If the wavelength always is a multiple of the distance between the fixed points.
What is the equation for the first harmonic?
1/ 2 x length x square root of tension / mass per unit length
What is the equation for mass per unit length?
mass / length
What affects the first harmonic?
- length
- tension
- mass per unit length
