All of AQA Waves Explained - A Level Physics REVISION

Waves

Oscillations of particles or oscillations of a field that can transfer or store energy.

Progressive wave

A type of wave that transfers energy.

Longitudinal wave

A type of progressive wave where particles oscillate in the same direction as the energy transfer.

Transverse wave

A type of progressive wave where particles oscillate at 90 degrees to the direction of energy transfer.

Amplitude

The height of a wave, equal on both longitudinal and transverse waves.

Wavelength

The distance from one wave to the equivalent point on the next wave, measured in peak to peak, trough to trough, or any point on the wave.

Time period

The time it takes for one complete wave cycle, denoted by capital T.

Frequency

The number of wave cycles per second, denoted by F, with the equation F = 1/T.

Phase

The part of the wave cycle that a wave is in, measured in degrees or radians.

Phase difference

The difference in phase between two parts of a wave or between two separate waves.

Longitudinal waves examples

Sound waves and ultrasound.

Transverse waves examples

Waves on a string and water ripples.

Polarization

The ability of transverse waves to be filtered based on the orientation of the oscillations.

Speed of light

The speed at which electromagnetic waves travel in a vacuum, approximately 3.00 x 10^8 meters per second.

Speed of a wave equation

The speed of a wave is equal to the frequency of the wave multiplied by the wavelength, denoted by C = F * λ.

Stationary wave

A wave that is formed when a progressive wave is reflected off a surface and interferes with the original wave, resulting in points of maximum and minimum displacement.

Node

A position in a stationary wave where there is no displacement, typically occurring at the fixed ends of a string or wave.

Anti-node

A point of maximum displacement in a stationary wave, typically occurring in the middle of a string or wave.

First harmonic

The fundamental frequency or mode of vibration in a stationary wave, characterized by one node at each end and one anti-node in the middle.

Interference

The phenomenon that occurs when two waves combine and interact with each other, resulting in either constructive or destructive interference.

Principle of superposition

The principle that states that when two waves meet, their displacements add together to produce a resultant wave.

Coherent

Waves that have the same frequency, wavelength, amplitude, and constant phase difference.

Path difference

The difference in distance traveled by two waves from their sources to a given point, which determines the type of interference (constructive or destructive) that occurs.

Phase difference

The difference in phase between two waves at a given point, measured in degrees or radians.

Frequency

The number of complete cycles or oscillations of a wave that occur in one second, measured in hertz (Hz).

Wavelength

The distance between two consecutive points in a wave that are in phase, typically measured in meters.

Tension

The force applied to a string or wave that determines its frequency and speed of propagation.

Mass per unit length

The mass of a string or wave per unit length, which affects its frequency and speed of propagation.

Diffraction

The bending or spreading out of waves as they encounter an obstacle or pass through an opening, resulting in the ability of waves to spread out and interfere with each other.

Laser light

Light amplification by the stimulated emission of radiation, characterized by being monochromatic and coherent.

Monochromatic

Having exactly the same wavelength or color.

Coherent

When waves have a constant phase difference and maintain a fixed relationship with each other.

Diffraction

The bending or spreading of waves as they pass through an opening or around an obstacle.

Fringes

The light and dark bands observed in a diffraction pattern.

Wavelength

The distance between two corresponding points on a wave, such as crest to crest or trough to trough.

Diffraction grating

A device with many closely spaced slits that produces a pattern of diffracted light.

Zeroth-order

The central bright spot in a diffraction pattern.

First-order, second-order, etc.

The bright spots in a diffraction pattern that are located at increasing angles from the central spot.

Path difference

The difference in distance traveled by two waves from a source to a point of observation.

Hypotenuse

The longest side of a right-angled triangle, opposite the right angle.

Trigonometry

The branch of mathematics that deals with the relationships between the angles and sides of triangles.

Refraction

The change in direction of a wave as it passes from one medium to another due to a change in speed.

Medium

A substance or material through which a wave travels.

Angle of incidence

The angle between the incident ray and the normal to the surface of the medium.

Angle of refraction

The angle between the refracted ray and the normal to the surface of the medium.

Refractive index

The ratio of the speed of light in a vacuum to the speed of light in a medium.

Snell's law

The relationship between the angles of incidence and refraction and the refractive indices of the two media.

Explain what happens when 2 coherent sources interfere Destructively

When 2 coherent sources interfere with a path difference of n(lambda) + lambda/2 waves have arrived in anti-phase and so a destructive interference pattern is observed and a small amplitude (or no amplitude) is observed.

Explain what happens when 2 coherent sources interfere Constructively

When 2 coherent sources interfere with a path difference of n(lambda) waves have arrived in phase and so a constructive interference pattern is observed and a large amplitude is observed.

3 Conditions for coherence

1. Same Frequency

2. Similar amplitude

3. In phase