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Physics > Yr 12 - Waves (2 of 2) > Flashcards

Yr 12 - Waves (2 of 2) Flashcards

1
Q

Order of EM spectrum (starting with largest wavelength & smallest Frequency)

A
  • Radio
  • Micro
  • Infrared
  • Visible
  • Ultraviolet
  • X-Rays
  • Gamma
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2
Q

Wavelengths for each em wave starting with greatest

A
  • Radio 10^5
  • Micro 10^-1
  • Infrared 10^-3
  • Visible 8x10^-7
  • Ultraviolet 4x10-7
  • X-rays 10^-8
  • Gamma 10^-12

All in meters

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3
Q

Frequencies for each em wave starting with the lowest.

A
  • Radio 10^3
  • Micro 10^8
  • Infrared 10^12
  • Visible 10^15
  • Ultraviolet 10^16
  • X-Rays 10^18
  • Gamma 10^20

All in hertz

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4
Q

Which type of waves can be polarised?

A

Transverse Waves only.

Longitudinal already in 1 plane.

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5
Q

What would a arrow diagram of each wave be like:

  • Polarised wave
  • Unpolarised
A
  • Arrow pointing in one straight direction only
  • Arrows pointing in every direction
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6
Q

Which type of waves used for thermal imagery & by rattlesnakes?

A

Infrared

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7
Q

Why is there a glare on a large body of water when the sun is shining?

A
  • Light from sun is unpolarised
  • When light hits water it is polarised
  • Some light is refracted into the water and the rest is reflected off the water.
  • Light reflected is polarised & glares due to high intensity in one plane.
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8
Q

What is a plane polarised wave?

A

A traverse wave oscillating in 1 plane.

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9
Q

What is the refractive index?

A

Ratio of speed of light in vacuum to speed in a substance.

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10
Q

Describe why a light wave refracts away/to from the normal the moving into a substance.

A

Less -> more dense
- Towards normal as wave hits substance at an angle and the side of wave that contacts first is slowed and therefore the wave (bends).

More -> less dense
- Away from normal (vice versa)

Think about it as a car going off-road at an angle

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11
Q

What is snells law?

A

n Sin𝞡 = constant

n sin(AOI) = n sin (AOR)

AOI = Angle of Incidence
AOR = Angle of refraction

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12
Q

Where are AOR & AOI measured from?

A

Both are measured from the normal

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13
Q

What is total internal reflection & when does it occur (angles)

A

Reflection of all light back into original medium

  • Occurs when AOI is greater than C
  • When AOI = C light directed along boundary

C = critical angle

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14
Q

What is an alternative (but similar) equation:

Sin C = 1 / n

A

Sin C = n2 / n1

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15
Q

What happens when light travels into:

  • Lower n
  • Higher n
A
  • Faster
  • Slower
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16
Q

Critical Angle

A

AOI that produces AOR of 90°

17
Q

What trait of a wave causes n to vary?

A

Frequency of the wave

18
Q

What is dispersion

A

Process of splitting white light
- Occurs due to varying wavelengths
- Shorter wavelength = greater dispersion (violet)

This is why different colours of light diffract less/more

19
Q

What is constructive interference

A

When 2 waves superpose in phase

20
Q

What is destructive interference

A

When 2 waves superpose in anti phase

21
Q

What is superposition? (Same as principle of superposition)

(superimposition is the same thing but less sciencey)

A

When 2 or more waves meet at a point & resultant amplitude is vector sum of individual amplitude.

22
Q

What is coherent?

A

2 or more waves that have:

  • Same wavelength
  • Constant phase difference
  • Same frequency

They do not have to be in phase.

23
Q

What is phase difference?

A

Fraction of a cycle between the same point on 2 different waves.

24
Q

What is path difference?

A

Difference in distance travelled by 2 coherent waves from different sources to a distinct point.

25
Q

Do waves have to be coherent to interfere?

A

Yes

26
Q

Can transverse and longitudinal waves interfere with each other?

A

Yes

27
Q

Explain Youngs double slit experiment including the key terms.

A

-> Slit separation = gap between slits next to light source
-> Separation distance = Distance between slit and screen
-> Fringe separation = distance between constructive fringes (Bright fringes)

28
Q

How and where to do measure fringe separation during Youngs double slit?

A

Measured from central fringe (N=0) then (N= +/- 1 etc)

Distance between constructive fringes. (bright spots)

Fringe seperation is constant.

29
Q

Whats the difference between a progressive and stationary wave?

A

Progressive waves transfers energy

Stationary waves store energy

30
Q

Order of wavelengths of light.

A

R - Long wavelength
O
Y
G
B
I
V - Short wavelength

31
Q

What is propagation?

A

Movement of waves

32
Q

What is wave form?

A

Displacement-Time graphs for waves

33
Q

Difference between nodes and antinodes

A

Node = 0 displacement / amplitude

Antinode = maximum displacement / amplitude

Node & Antinode are 1/4 wavelengths apart

34
Q

How are stationary waves formed?

A

By superposition of 2 progressive waves in opposite directions.

  • No net transfer of energy
  • Same frequency
35
Q

What is the fundamental frequency?

A

Lowest possible frequency where a system can vibrate to create a stationary wave.

36
Q

What is a harmonic?

A

An integer multiple of the fundamental frequency.

37
Q

Closed end vs open end

A

Closed end = node
Open end = antinode

38
Q

What are the first 4 harmonics in terms of wavelengths?

A

1st = 1/4 wavelengths
2nd = 1/2 wavelengths
3rd = 3/4 wavelengths
4th = 1 wavelength

39
Q

Progressive wave vs standing wave

A

Progressive

  • Energy transferred along it (flicking a string up and down)

Standing ]

  • Points of max & min energy (nodes & antinodes)

Physics (18 decks)

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