# Unit 1 Physics: Waves in Communication

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Frequency
The number of oscillations (vibrations) per second.
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Periodic time
The time taken to complete one oscillation.
periodic time= 1/ frequency
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Amplitude
The largest distance between the point that the wave moves from its rest position.
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Wavelength
The distance between two adjacent wavefront peaks.
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Wave speed
The speed that it takes the wave to travel to a given point in a period of time.
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Phase
Describes how far through a cycle a wave is.
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Phase difference
A measure of the difference in where two waves are in their cycle.
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Transverse waves
When particles in the medium vibrate at right angles to the direction of the wave's motion.
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Longitudinal waves
When the medium's particles vibrate in the same direction as the wave's motion.
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Stationary wave
When two progressive waves (same wavelength/ frequency) move in opposite directions, interfering with eachother.
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Node
A point on a stationary wave that have zero amplitude.
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Anti-node
A point which oscillate from the furthest point upwards to the furthest point downwards.
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Electromagnetic waves
Vibrating electrical/ mechanical fields that travel through space with no medium.
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Displacement
The distance at any given moment from the central/ equilibrium position.
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Path difference
The number of cycle's difference there's between two waves from the same source.
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Refraction
When light enters a more dense medium and bends towards the normal.
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Diffraction
The spreading of waves when they pass through a gap or move past an obstacle.
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Reflection
The change in the direction of a wave that can either be light or sound, away from the wave boundary.
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Specular reflection
Defined as light reflected from a smooth surface at a definite angle.
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Diffuse reflection
Waves that are produced by rough surfaces that tend to reflect light in all directions.
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Superposition
The net displacement of the medium at any point in space or time, is simply the sum of the individual wave displacements.
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Constructive interference
When both waves have the same sign displacement.
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Destructive interference
At the point of overlap, if the waves have opposite displacements, they will cancel eachother out.
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Coherent
The superposition of the waves gives a visible interference pattern.
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Single slit diffraction
When light passes through a narrow slit, a pattern of alternate bright and dark fringes are produced.
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Resonance
When an object is made to oscillate at its natural frequency, it creates large amplitude oscillations.
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Optical density
The degree at which the light refracts through a medium.
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Refractive index
A number that denotes how light passes through a medium/ how much light is refracted.
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Total internal reflection
Complete reflection of a light ray reaching a boundary greater than the critical angle.
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Optical fibres
Used to transmit light, communication and medicinal applications; cylindrical core of glass encased in glass cladding.
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Analogue signals
Signals that continuously vary in frequency and amplitude.
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Digital signals
Signal of a sequence of discrete values (either 0 or 1).
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## Other cards in this set

### Card 2

#### Front

The time taken to complete one oscillation.
periodic time= 1/ frequency

Periodic time

### Card 3

#### Front

The largest distance between the point that the wave moves from its rest position.

### Card 4

#### Front

The distance between two adjacent wavefront peaks.

### Card 5

#### Front

The speed that it takes the wave to travel to a given point in a period of time.