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Council Phys > Progressive and stationary waves > Flashcards

Progressive and stationary waves Flashcards

1
Q

displacement

A

distance and direction an oscillating particle moves from its rest position
metre (m)

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2
Q

amplitude A

A

maximum displacement an oscillating particle in the medium moves from its rest position
metre (m)

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3
Q

wavelength , lambda

A

distance between any point on a wave to an adjacent one that is exactly in phase with it
metre (m)

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4
Q

period T

A

time taken for one complete wave to pass a fixed point
second (s)

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5
Q

frequencyf

A

number of complete
waves passing a fixed point per second
hertz (Hz)

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6
Q

define the PHASE of a particle on a wave

A

the phase of a particle on a wave is the fraction of a cycle it has completed since the start of the cycle.

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7
Q

define the PHASE DIFFERENCE of two particles?

A

the phase difference of two particles on a wave, or on two waves is the fraction of a cycle by which their oscillations are separated.

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8
Q

what can phase difference be expressed in?

A

-fraction of the wavelength, lambda
-in degrees
-in radians

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9
Q

how many degrees and radians is 1 cycle?

A

1 cycle or 1 lambda = 360° = 2 π radians

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10
Q

if two points on a wave are separated by a horizontal distance, d ….. what’s is the phase difference in radians?

A

phase difference in radians= 2 πd/ wavelength

ONLY FOR PROGRESSIVE WAVES

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11
Q

what is a WAVEFRONT ?

A

a wavefront is a line or a surface on which the vibrations of the medium all have the same phase at all points.

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12
Q

how to convert between degrees and radians?

A

x 180/π
____>

π = 180

< ____
x π/180

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13
Q

how many degrees is 1 radian?

A

360° = 2 π radians
360°/ 2π = 1 radian
57.3° = 1 radian

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14
Q

how many radians is 90°?

A

π / 2

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15
Q

how many radians is 180°?

A

π

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16
Q

how many radians is 270° ?

A

3 π/ 2

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17
Q

how many radians is 360° ?

A

2 π

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18
Q

what are waves caused by?

A

Waves are caused by something oscillating the particles in the medium (or oscillating the field) through which the wave travels.

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19
Q

what is a PROGRESSIVE wave?

A

A progressive wave transfers energy from one place to another without transferring matter.

20
Q

what equation are frequency and period related by

A

f= 1/T

21
Q

what equation are the speed, frequency and wavelength of a wave related?

A

wave speed c = f x lambda

22
Q

what are mechanical waves?

A

Mechanical waves require a physical substance to move through.

23
Q

what are electromagnetic waves?

A

Electromagnetic waves can travel through a vacuum - they are oscillations in electric and magnetic fields that permeate space. All electromagnetic waves travel at the same speed in a vacuum:
3.00X109 m/s

24
Q

what are longitudinal waves?

A

Longitudinal waves - oscillations of the medium are parallel to the direction of energy transfer. For example, sound waves.

25
Q

what are transverse waves?

A

Transverse waves - oscillations of the medium are perpendicular to the direction of energy transfer. For example, electromagnetic waves and waves on a string.

26
Q

what is the principle of superposition?

A

The principle of superposition states that when two waves meet, the total displacement at a point is equal to the sum of the individual displacements at that point.

27
Q

what is reinforcement?

A

It two waves meet exactly in phase, they will add together CONSTRUCTIVELY to form a double height wave (reinforcement)

28
Q

what is cancellation?

A

It two waves meet exactly out of phase (antiphase), they will add together DESTRUCTIVELY and cancel each other out

29
Q

what is polarisation?

A

when the oscillation of a a transverse wave are restricted into a single plane, they are polarised.

30
Q

if a wave can be polarised, it must be…

A

a transverse wave (longitudinal waves can’t be polarised)

31
Q

how do transverse waves passing through a slit on a board become polarised?

A

only oscillations parallel to the slit pass through it

32
Q

how are glares caused?

A

Light reflected from some surfaces (wate/ glan) is partially polarised. this reflected light causes glare.

33
Q

how can glare be reduced?

A

by filtering out the polarised light using polarising filters

34
Q

how is a stationary wave formed?

A

A stationary wave is formed when two progressive waves with the same frequency and amplitude, moving in opposite directions, superpose.

35
Q

how are stationary waves most commonly formed?

A

Stationary waves are often the result of the reflection of a progressive wave superposing with the original wave.

36
Q

what is a node?

A

A node is a point where there is no oscillation - the two waves always meet with a phase difference of 180° (pi radians).

37
Q

what is antinode?

A

An antinode is a point where oscillation is at maximum amplitude - the two waves always meet in phase at that point.

38
Q

distance between two nodes in a stationary wave is

A

distance between two node = 1/2 wavelength

39
Q

what does it mean when all the point between two nosed oscillate in phase…

A

All the points between two nodes oscillate in phase, meaning they reach their maximum displacements at the same time.

40
Q

do stationary waves that oscillate freely transfer energy to their surrounding?

A

Stationary waves that oscillate freely do not transfer energy to their surroundings. When stationary waves are formed:
• by sound waves, there is silence at the nodes and maximum volume at the antinodes
• in a microwave oven, there is no heating at the nodes, and maximum heating at the antinodes.

41
Q

describe the first harmonic

A

The first harmonic:
As the frequency of oscillation is increased from zero, the first harmonic is seen at the lowest frequency that gives a pattern.

42
Q

what equation is The frequency f of the first harmonic related to the length l, tension T, and mass per unit length u of the string by ?

A

f = 1/2 l square root (T/u)

43
Q

describe the second and third harmonic….

A

The second harmonic occurs at twice the frequency of the first harmonic; the third harmonic occurs at three times the frequency of the first harmonic; etc.

44
Q

what is the wavelength and frequency at the first harmonic?

A

wavelength= 2L (length of string)
frequency= f0

45
Q

what is the wavelength and frequency at the second harmonic?

A

wavelength= L
frequency= 2f0

46
Q

what is the wavelength and frequency at the third harmonic?

A

wavelength = 2L/3
frequency = 3f0

Council Phys (3 decks)

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