# AS Physics - Waves and Quantum Physics Key Words

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Wave
A series of oscillations/vibrations that transfer energy (not matter) from one place to another.
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Transverse wave
A wave where the direction of energy transfer is perpendicular to the individual oscillations of the particles.
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Longitudinal wave
A wave where the direction of energy transfer is parallel to the individual oscillations of the particles.
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Progressive wave
A wave that transfers energy away from a source.
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Wavelength (λ)
The distance between two similar consecutive points on a wave.
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Time period (T)
The time it takes for one complete pattern of oscillations to take place at any point.
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Frequency (f)
The number of wavelengths passing a point per unit time.
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Displacement (s)
The distance any part of a wave has moved from its mean (or rest) position.
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Amplitude (A)
The maximum displacement of a wave. It is the distance between the mean position and the peak/trough.
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Wave speed (v)
The speed of the wave.
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Phase (ϕ)
The fraction of one complete wave cycle (or the fraction of one complete oscillation)
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Phase difference
The difference in the fraction of a cycle of oscillations between two points on the same wave of the same point on two different waves.
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Intensity
The rate at which energy is transferred from one location to another as a wave travels through space, perpendicular to the direction of wave travel.
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Refraction
The changing of wave speed and wavelength of a wavelength of a wave as it travels from one medium to another.
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Diffraction
The spreading out of waves as they pass through a gap or around an obstacle.
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Interference
The addition of two or more wave that results in a new wave pattern.
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Plane-polarised wave
A wave where the oscillations of the field and the direction of travel are confined to a single plane.
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Polarising filter
A filter that produces plane-polarised light by selective absorptions of one component of the incident oscillations.
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Refractive index
The speed of light in a vacuum divided by the speed in which light travels in the material.
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The Principle of Superposition
When two or more waves meet, the displacement of the resultant wave is equal to the sum of the displacement of the individual waves.
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Coherence
When two waves have constant phase difference.
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Constructive interference
When two waves meet in phase (0°/0 rad phase difference) and the resultant wave has a maximum amplitude.
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Destructive interference
When two waves meet with a phase difference of 180°/π rad and the resultant wave has a minimum amplitude.
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Order of maximum
The number of the pattern, n, on either side of the central maximum.
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Central maximum
The maximum amplitude formed in Young's Slits/diffraction grating where the two waves have travelled exactly the same distance and interfere constructively.
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Stationary wave
A wave formed when a progressive wave is reflected and the incident wave and reflected wave interfere.
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Antinode
The point on a stationary wave with maximum displacement.
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Node
The point on a stationary wave with minimum displacement.
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Fundamental frequency
The frequency of a stationary wave in its fundamental mode of vibration (for a string this is where L = ½λ)
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nth harmonic
A stationary wave with frequency n times larger than its fundamental frequency.
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Quantum
A small discrete unit of energy.
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Photon
An individual packet of energy of electromagnetic radiation that behaves like a particle.
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Planck's constant (h)
6.63×10^(-34)Js, a multiple which photon energies are always emitted in.
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Electron-volt
The energy gained by one electron when it moves through a potential difference of 1 volt.
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Threshold frequency (f_0)
The minimum frequency of electromagnetic radiation required to remove an electron from the surface of a particular metal, without giving it any kinetic energy.
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Work function (Φ)
The minimum energy to remove an electron from the surface of a particular metal.
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Stopping voltage (V_0)
The potential difference required across a photocell to stop electrons getting across.
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Wave-particle duality
The concept that under certain circumstances, waves can behave like particles and particles can behave like waves.
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## Other cards in this set

### Card 2

#### Front

A wave where the direction of energy transfer is perpendicular to the individual oscillations of the particles.

Transverse wave

### Card 3

#### Front

A wave where the direction of energy transfer is parallel to the individual oscillations of the particles.

### Card 4

#### Front

A wave that transfers energy away from a source.

### Card 5

#### Front

The distance between two similar consecutive points on a wave.