Unit 2 Topic 2 - Waves

Wave

A disturbance or oscillation in particles that results in the transfer of energy from on place to another.

Mechanical wave

A wave that requires a medium to propagate

Electromagnetic wave

A wave that does not require a medium to travel

Propagation

The way waves travel and spread energy throughout space or a medium, often referring to direction.

Wavelength

The distance between corresponding points on a successive wave EG peak to peak, through to trough.

Amplitude

The maximum displacement from the equilibrium.

Crest/peak

The highest point the wave reaches above the middle point.

Trough

The lowest point a wave goes below the medium.

Medium

A material or substance that carries energy from one place to another.

Frequency

The number of waves that move past a point in one second.

Period

The time, in seconds, it takes for one wave to be completed.

Transverse wave

A wave where the oscillation of particles is perpendicular to the medium, including all waves on the electromagnetic spectrum.

Pulse

An isolated, single disturbance that travels through a medium

Periodic wave

A continuous, repeating series of disturbances within a medium, travelling with constant speed.

Longitudinal wave

A wave where the oscillation of particles is parallel to the medium, including all sound waves.

Compressions

Areas of a longitudinal wave that have high particle density.

Rarefactions

Areas of a longitudinal wave that have low particle density.

Velocity (formula)

The frequency of the waves times by the wavelength.

Polarisation

The restriction of the directions of oscillation for transverse waves.

Angle of incidence/reflection

The angle of incidence is the angle at which light approaches an object relative to the normal, and the angle of reflection is the angle at which light travels away from an object compared to the normal.

Law of reflection

States that the angle of incidence is equal to the angle of reflection when compared to the normal.

Refraction

The principle that light is deflected while passing through the interface between one medium and another.

Snell's law

n1Sin(i) = n2Sin(r), where n is the refractive index of the respective object, i is the angle of incidence and r is the angle of refraction.

Diffraction

The bending of waves around obstacles or the spreading of waves as they pass through small openings.

Wavefront

A surface over which an oscillation or wave phase is constant.

Huygen's principle

Every point on a wavelength acts as a source of secondary spherical wavelets.

Factors affecting diffraction

Longer wavelengths diffract more than shorter wavelengths and smaller apertures cause greater diffraction.

Principal focus

A specific point on the principal axis where parallel light rays converge or appear to diverge.

Principle of superposition

The overall displacement between two colliding waves is the sum of the individual displacements of the contributing waves.

Constructive interference

When peak of one wave lines up with the peak of another, resulting in higher amplitudes.

Destructive interference

When peak of one wave lines up with the trough of another, resulting in cancellation of amplitudes.

Standing waves

A wave pattern formed by identical waves traveling in opposite directions; length must be a multiple of ½ λ.

Forbidden standing waves

Waves that collapse if their wavelength does not match the space containing the wave.

Nodes

Points along a standing wave that remain stationary due to the cancellation of amplitudes.

Antinodes

Points along a standing wave created by adding amplitudes, alternating between maximum and minimum.

Wave speed

V = fλ in one dimension, where v is speed, f is frequency in hertz, and λ is wavelength.

Harmonic frequency

The frequency produced by the natural vibrations in objects.

Fixed end waves

A wave that reflects backwards upside down from a fixed boundary, creating a standing wave with nodes and antinodes.

Resonance

Vibrating with maximum amplitude when exposed to a wave that matches its natural frequency.

Free vibrations

Vibrations that occur naturally in a system without external driving forces.