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as physics module 4 > module 4.4 waves mock revision > Flashcards

module 4.4 waves mock revision Flashcards

1
Q

Progressive Wave

A

A series of vibrations that transfers energy from one place to another.

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2
Q

Longitudinal Wave

A

A wave where particle oscillations are in the direction of wave propagation. E.g. Sound Waves

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3
Q

Transverse Wave

A

A wave where particle oscillations are perpendicular to the direction of wave propagation

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4
Q

Displacement

A

The distance any part of a wave has moved from its mean or rest position

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5
Q

Amplitude

A

The maximum displacement of a wave from its mean or rest position

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6
Q

Wavelength

A

The smallest distance between two points on a wave that are in phase

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7
Q

Period

A

The time taken for one complete pattern of oscillation

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8
Q

Frequency

A

The number of oscillations at a given point per unit time

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9
Q

Speed of a wave

A

Distance travelled by the wave (energy) per unit time

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10
Q

frequency = 1/period

A

period = 1/frequency

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11
Q

𝑆𝑝𝑒𝑒𝑑(𝑣) =𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 (𝑑)/ 𝑇𝑖𝑚𝑒 (𝑡)

A

→ 𝑆𝑝𝑒𝑒𝑑(𝑣) = 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑀𝑜𝑣𝑒𝑑 (𝜆) /𝑇𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛 (1/𝑓)

v = 𝑓𝜆

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12
Q

Reflection

A

When waves rebound from a barrier, changing direction but remaining in the same medium.

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13
Q

Refraction

A

When waves change direction when they travel from one medium to another due to the difference in wave speed in each medium.

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14
Q

Diffraction

A

When a wave spreads out after passing around an obstacle or through a gap

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15
Q

radio waves

A

used for communication, tv radio

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16
Q

microwaves

A

used in mobile phones, microwave ovens,

communication, heating

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17
Q

infrared

A

heating, remote controls

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18
Q

visible light

A

sight

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19
Q

uv

A

tanning, counterfeit detection

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20
Q

x-rays

A

x-ray photography, security scanners, kill cancer cells

21
Q

gamma rays

A

cancer treatmet, sterilisation of medical instruments

22
Q

gamma rays

A

cancer treatment, sterilization of medical instruments

23
Q

the role of sunscreen

A

Protects the skin from sunburn by absorbing UV-B radiation

UV-B also produces vitamin D

24
Q

All electromagnetic have some properties in common

A

They all travel at the speed of light in a vacuum and slower speeds in other media

They are transverse waves consisting of vibrating electric and magnetic fields. The electric and magnetic fields are at right angles to each other and the direction of travel.

Like all waves they can be reflected, refracted and diffracted and can undergo interference.

Like all ways they obey v=fλ (v = velocity, f = frequency, λ = wavelength)

Like all progressive waves, progressive EM waves carry energy

Like all transverse waves EM waves can be polarised

25
Q

Some Properties Vary Across the EM Spectrum

A

The longer the λ the more obvious the wave characteristics

Energy is directly proportional to the frequency (E = hf)

The higher the energy the more dangerous the wave

The lower the energy the further from the nucleus it comes from.

  • Gamma radiation comes from inside the nucleus.
  • X-rays to visible light come from energy level transitions in atoms.
  • Infrared radiation and microwaves are associated with molecules.
  • Radio waves come from oscillations in electric fields.
26
Q

Plane-Polarised Wave

A

A transverse wave oscillating in only one plane

27
Q

Polarisation

A

The process of turning an un-polarised wave into a plane polarised wave.

28
Q

wave phenomena that apply to both longitudinal and transverse waves

A

diffraction

refraction

superposition (interference)

29
Q

a wave phenomenon that applies only transverse waves but not longitudinal waves.

A

Polarisation

30
Q

how polaroid sunglasses can prevent glare from light reflected from a water surface

A

light reflected from water surface is partially plane polarised

alignment of polaroid lens is at right angles to plane of polarisation of reflected light

polarised reflected light is not transmitted by polaroid lens

31
Q

Malus’s law

A

A = A0Cosθ so I = I0Cos2θ

I = 1/2I0 after first filter as ½ light goes through.

32
Q

Describe and explain an experiment to demonstrate the polarisation of microwaves

A

place microwave transmitter and receiver facing each other

place two polarising filters (metal grid with bars ~1cm apart) across path of beam

observed signal on receiver is maximum intensity when polarising filters are parallel

the first filter polarises the beam, the beam can pass through the second filter because the plane of polarisation of the beam matches the alignment of the filter.

rotate polarising filter 90^ from parallel to crossed
observed signal on receiver drops to minimum intensity (zero) when polarising filters are
crossed

the beam cannot pass through the second filter when the plane of polarisation of the beam is at 906^ to the alignment of the filter

33
Q

Principle of Superposition

A

When two or more waves meet at a point the resultant

displacement at that point is the vector sum of the displacements due to each wave.

34
Q

Interference

A

The vector addition of two or more waves (superposition) that results in a new wave pattern

35
Q

Coherence

A

Two waves with a constant phase relationship (Same f & λ)

36
Q

Phase Difference (φ)

A

The angular distance by which one particle leads or lags behind another particle in its pattern of oscillation.

37
Q

Path Difference

A

The distance between the distances travelled from their sources by two waves meeting at a point.

38
Q

Constructive interference

A

If two waves exist at the same point and are in phase, the amplitude of the resultant wave will be the sum of the amplitudes of the individual waves

39
Q

Destructive interference

A

If two waves exist at the same point and are anti-phase, the amplitude of the resultant wave will be zero as the waves cancel each other out.

40
Q

𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 =

A

𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = 𝑃𝑜𝑤𝑒𝑟/ 𝐶𝑟𝑜𝑠𝑠 𝑆𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝐴𝑟𝑒𝑎

𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 ∝ 𝑎𝑚𝑝𝑙𝑖𝑡𝑢𝑑𝑒2

41
Q

n = d sin 0

A

n is order of maximum [ no units ]

λ = wavelength [ m ]

d is spacing between slits [ m ]

0 is angle at which maximum occurs [ degrees ]

42
Q

Node

A

A point that always has zero amplitude along a stationary wave, caused by destructive interference

43
Q

Antinode

A

A point of maximum amplitude along a stationary wave, caused by constructive interference

44
Q

Fundamental Mode of Vibration (Frequency)

A

The lowest frequency in a harmonic series where a stationary wave forms.

45
Q

Harmonics

A

Stationary waves for a particular system with higher frequencies than the fundamental.

46
Q

how a stationary wave is formed

A

wave travels to end and is reflected

reflected wave superposes with incident wave to produce a resultant wave

at certain points always destructive interference to produce nodes

at certain points always constructive interference to produce antinodes

47
Q

phase difference

A

how far ‘out of step’ the oscillations at two points

on the wave are

48
Q

stationary wave

A

a wave which traps/stores energy (in pockets)

has nodes and antinodes

49
Q

how is a stationary wave formed

A

the wave is reflected

it interferes/superposes with the incident wave
to produce a resultant wave with nodes and antinodes/no energy transfer

as physics module 4 (5 decks)

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