What is a progressive wave?
A wave where energy is transferred without transferring material, made up of oscillating particles.
What is amplitude?
A wave’s maximum displacement from the equilibrium position.
What is frequency?
The number of complete oscillations passing through a point per second.
What is wavelength?
The length of one whole oscillation (the distance between two adjacent peaks/troughs.
What is wave speed?
The distance travelled by the wave per unit time.
What is phase?
The position of a certain point on a wave cycle.
What is phase difference?
How much a particle/wave lags behind another particle/wave.
What is the period of a wave?
The time taken for one full oscillation.
When are two points on a wave in phase?
When their phase difference is a multiple of 360 degrees or 2 pi radians.
When are two points on a wave in antiphase?
When their phase difference is an odd multiple of 180 degrees/pi radians.
What are transverse waves?
Waves where the particles oscillate perpendicular to the direction of energy transfer, such as electromagnetic waves.
What are longitudinal waves?
Waves where the particles oscillate parallel to the direction of energy transfer, such as sound waves.
What is polarisation?
When the oscillations of a transverse wave are confined to a single plane.
What is superposition?
When the displacements of two waves are combined as they pass each other.
What is constructive interference?
This occurs when two waves are in phase, or have displacement in the same direction. The displacements of the wave are added.
What is destructive interference?
When two waves have opposite displacements/are in antiphase, so they cancel each other out.
What is a stationary wave?
A wave formed from the superposition of two progressive waves, which doesn’t transfer any energy.
How is a stationary wave formed?
A progressive wave hits a boundary, and is reflected. The original and reflected waves meet and superpose. Where the waves meet in phase, constructive interference occurs, forming antinodes. Where the waves meet in antiphase, destructive interference occurs and nodes are formed.
What is path difference?
The difference in the distance travelled by two waves.
When is a wave/light source coherent?
When it has the same frequency and wavelength, and a fixed phase difference. Coherent light sources are typically monochromatic.
What does Young’s double slit experiment demonstrate?
Interference of light from two sources.
When are maxima formed?
When the path difference between two adjacent waves is a whole number of wavelengths, so the waves interfere constructively.
When are minima formed?
When the path difference between two adjacent waves is an odd number of half wavelengths, so the waves interfere destructively.
