# AS Physics Waves

Define Wave
A disturbance which can travel, using transferring energy
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Define Wave Speed
Distance travelled by a wave front per unit time
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Define Continuous Wave
In a full cycle of vibration, one point in the medium moves from its equilibrium position to one extreme to the other extreme and back to the equilibrium position
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Define Transverse Waves and give an example
The direction of vibration is at 90 degrees to the dicrection the wave is travelling e.g light (EM) or a wave on a string
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Define Longitudinal Waves and give an example
Medium ocillates parallel in the same direction the wave is travelling e.g. primary seismic waves or sound
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Define Mechanical Waves and give an example
Require a medium to travel e.g. water waves
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What is Displacement of a Point in the Medium?
It's distance and direction from its equilibrium point
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What is Frequency of Vibration?
The number of cycles of vibration in one second measured in Hz
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What is Time Period?
Time taken for one cycle of vibration
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What does In Phase mean?
Describes two points in the medium that are moving in the same direction and change direction at the same point
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Define Wavelength
The distance between two consecutive points that are in phase
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Define Amplitude
The maximum displacement of a vibrating point in the medium
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Define Phase Difference
The amount by which one vibration lags behind another measured in degrees
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What is the Wave Speed equation?
Wave Speed= Frequency x Wavelength
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Define Refraction
The bending of a wave due to change of speed
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Define Diffraction
The bending of waves as they pass through a gap or pass by an obstacle
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When does maximum diffraction occur?
When the gap size is similar to the wavelength
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Define Principle of Superposition
At a point where two waves meet, the total displacement is the sum of the displacements due to the individual waves
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What happens when the waves from two machines meet?
They pass through each other, but, when they overlap they combine; when a crest meets a crest a double sized crest is produced, when a trough meets a trough a double sized trough is produced. But when a crest meets a trough they cancel each other out
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What is the pattern produced by two wave sources that are side-by-side?
Interference Fringes
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What kind of interference is superposition?
Constructive
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What kind of interference is crest + trough?
Destructive
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Define Coherent Sources
Sources which are positioned side by side; they have the same frequency and are vibrating in phase
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Define Path Difference
Extra distance travelled by the wave from one source compared with the wave from the other source
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What is Fringe Spacing?
The distance from the centre of one bright fringe to the next
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What is the Fringe Spacing equation?
W = (wavelength x distance from slits to screen)/slit seperation
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What is the Grating equation?
n x wavelength = dsin(angle)
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What do diffraction and interference experiments tell us about the nature of light?
Light can undergo double slit interference and diffraction with a grating shows us that light has wave-like properties
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How do we know that light behaves like a Transvers Wave?
We can polarise light
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Define Polarisng Filter
The transmission axis of a polarising filter is the direction of the vibrations that it will transmit
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Define Unpolarised Light
Has vibrations in many directions (but all still at 90 degrees to the direction of travel)
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Define Plane Polarised Light
Has vibrations in only one direction
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Can Longitudinal Waves be polarised?
No
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Define Stationary Waves
Points on a medium (e.g. string) that don't move
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What do you need to form Stationary Wave Patterns?
Need two waves that have the same speed, wavelength, and frequency and approximately the same amplitude,
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How are Stationary Wave Patterns formed?
The incident wave travels along the string to the opposite end where it is reflected. The superposition of the incident and reflected wave creates a SWP
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What happens at Nodes?
The incident and reflective waves interfere destructively
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What happens at Antinodes?
The incident and reflected waves interfere constructively
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What is the Node-Node seperation?
1/2 x wavelength
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What do adjacent node-node loops vibrate at?
180 degrees (A.K.A anti-phase)
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## Other cards in this set

### Card 2

#### Front

Define Wave Speed

#### Back

Distance travelled by a wave front per unit time

### Card 3

#### Front

Define Continuous Wave

#### Back ### Card 4

#### Front

Define Transverse Waves and give an example

#### Back ### Card 5

#### Front

Define Longitudinal Waves and give an example

#### Back 