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Physics M4 (electrons, waves, photons) > 11. Waves > Flashcards

11. Waves Flashcards

1
Q

Define a progressive wave

A
  • An oscillation (vibration) that transfers energy but does not transfer matter
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2
Q

Deinfe mechanical waves

A
  • Progressive waves that need a medium to travel through
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3
Q

Define electromagnetic waves

A
  • Progressive waves that can travel through a vacuum
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4
Q

Examples of mechanical waves

A
  • Sound waves
  • Tidal / water waves
  • Seismic waves
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5
Q

Examples of electromagnetic waves

A
  • Radio waves
  • Microwaves
  • Infrared
  • Ultralight
  • Visible
  • Xrays
  • Gamma rays
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6
Q

What are mechanical waves composed of?

A

Mechanical waves are composed of the movement of matter that transfer energy

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7
Q
A
  • As the progressive wave travels through the medium (material) the particles move from their equilibrium position
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8
Q

Define transverse waves

A
  • When energy is transported perpendicular to the direction of oscillation
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9
Q

Define longitudinal waves

A
  • When energy is transported parallel to the direction of oscillation
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10
Q

Describe the characteristics of a wave diagram

A
  • Compression IIIIIIII
  • Oscillation <——–>
  • Rarefaction I I I
  • Energy ——->
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11
Q

Name examples of longitudinal waves

A
  • Sound waves
  • P-waves in earthquakes
  • Pressure waves
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12
Q

Name examples of transverse waves

A
  • EM waves
  • Water waves
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13
Q

Describe the similarities and differences between transverse and longitudinal waves

A
  • Both transfer energy
  • Transverse requires a medium, logotidom
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14
Q

Define wavelength (lamda)

A
  • The minimum distance between two points in a phase on adjacent waves
  • Units are metres
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15
Q

Define wave displacement (s)

A
  • Distance from the equilibrium position in a particular direction; a vector, so it can have either a positive or negative value
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16
Q

Define amplitude (A)

A
  • Maximum displacement from its equilibrium position
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17
Q

Define frequency (f)

A
  • Number of waves passing a point per unit time
  • Units are Hertz or per second
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18
Q

Define time period (period of oscillation) (T)

A
  • The time taken for a wave to move past a given point or the time taken for one oscillation
  • Units are seconds
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19
Q

Describe the relationship between frequency and time period

A
  • They are inversely proportional
  • f= 1/T
20
Q

State the equation for wave speed

A
  • v = wave length x frequency
21
Q
A

Waves are oscillations therefore we describe the difference between waves with the use of angles in radians
π = 180 degrees

22
Q

Define in phase

A
  • When a part of the wave continually has the same displacement
  • The wave will have a phase difference of 0 or multiples of 2π radians
23
Q

Define anti phase

A
  • When a part of the wave continually has the opposite displacement
  • The wave will have a phase difference of π radians
24
Q

State the phase difference equation

A
  • The phase difference
    pitchfork = x/lamda x 360
25
Q

Define a ray

A
  • A representation of a wave
  • A straight line with an arrow indication the direction of energy transport
26
Q

Define reflection

A
  • Occurs when a wave changes direction at a boundary between two materials
27
Q

Define refraction

A
  • Occurs when a wave changes direction and speed when passing from one material to another
28
Q
A
  • Reflection and refraction both occur when a wave changes direction at boundaries of different mediums
    *
29
Q

law and rules of reflection

A
  • ø incidence = ø reflection
30
Q
A
  • When waves reflect their wavelength and frequency do not change
  • A reflected wave gains an additional 90˚ phase difference from the incident wave
31
Q
A
  • Refraction is when the wave changes velocity (speed and direction)
  • If the refracted ray bends towards the normal the wave has slowed down
  • When the refracted ray bend away its speed has increased
32
Q
A

1) Start with absolute uncertainty
2) Calculate uncertainties in quantities plotted
3) Uncertainty bars for x and y (vertical box plot)

33
Q

Diffraction and direction

A
  • When a wave passes through a gap they spread out, this is diffraction
  • All waves can undergo diffraction
  • The speed, wavelength and frequency of a wave does not change when diffraction occurs
  • Diffraction only affects the waves direction
34
Q

The magnitude of diffraction

A
  • The amount of diffraction depends upon two quantities
  • Wavelength of a wave
  • Size of gap (or obstacle)
35
Q
A
  • Diffraction is increased when the size of the gap is comparable to the wavelength of the wave
36
Q
A
  • The relative size of a doorway and the wavelengths of light and sound is why you can hear someone around a doorway but you cannot see them
37
Q
A
  • Diffraction - only direction changes
  • Refraction - refraction, velocity and frequency changes
38
Q
A
  • Wavelength of sound is compared to width of the door
39
Q

Polarisation

A
  • Waves are oscillations that transfer energy
  • To date we have only considered waves that oscillate in one dimension
  • Yet we live in a three dimensional world so it makes sense that the oscillations can be in three dimensions too
40
Q

Define plane polarised waves

A
  • Waves that oscillate in one plane (one dimension)
41
Q

Define unpolarised waves

A
  • Waves that oscillate in many possible planes
42
Q

Is light from a filament lamp polarised or unpolarised?

A
  • Unpolarised
43
Q

Can longitudinal waves be plane polarised?

A
  • The direction of energy transport is parallel to oscillation
  • As their oscillations are limited to on plane it does not make sense to talk about them being plane polarised
  • Therefore, we say longitudinal waves cannot be plane polarised
44
Q

Reflected partial polarisation

A
  • When transverse waves reflected off a surface they become partially polarised
  • This means there are more waves oscillating on one particular plane but no completely plane polarised
45
Q
A
  • Unpolarised light - possible planes of oscillations
  • Partial polarised light - Majority of oscillations in this plane
46
Q

I = P/A

A
47
Q
A

Physics M4 (electrons, waves, photons) (5 decks)

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