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Physics > unit 2 wave ( standing wave ) > Flashcards

unit 2 wave ( standing wave ) Flashcards

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1
Q

stationary wave

A

is a disturbance / oscillations that do not transfer energy in the direction of the wave although it does have energy associated with it

  • consists of 2 identical travelling waves going in opposite directions
  • net effect is no energy transfer
  • example : resonance
  • fundamental and harmonics frequencies are the different values of natural frequency of the oscillating system
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2
Q

formation of stationary waves

A
  1. when two waves which are the same type
  2. travelling in opposite directions
  3. share the same speed and frequency
  4. approximately equal amplitude are superposed
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3
Q

two ways to produce identical waves travelling in opposite direction

A
  1. produce the wave directly , sending from opposite directions down a medium ( spring or string )
  2. send one wave down and observe it crossing its own returning reflection
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4
Q

superposition

of 2 such waves resulta in

A

points where the displacement is always zero - nodes

midway between nodes are points where always maximum displacement / amplitude are greater than anywhere else - antinodes

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5
Q

node

A

a point on a stationary wave where displacement is always zero

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6
Q

antinode

A

a point on a stationary wave that oscillates with max amplitude

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7
Q

the position of nodes and antinodes on axis do not change

adjacent nodes / adjacent antinodes are…. apart

A

1/2 wavelength apart

wavelength = 2 times distance between 2 adjacent nodes / antinodes

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8
Q

amplitude of travelling wave

A

1/2 times amplitude of stationary wave

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9
Q

motion of stationary wave ( particles )

draw out

A

pg 32`

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10
Q

motion of stationary wave ( particles )

-within one loop all particles

A

oscillates in phase but with diff amplitudes

all particles within the loop have their max displacement simultaneously

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11
Q

motion of stationary wave ( particles )

-oscillations in one loop are in what phase with those in adjacent loop

A

antiphase

particles on either side of a node moves in opposite direction

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12
Q

motion of stationary wave ( particles )

- particles adjacent to a node with equal distance from the node have same amplitude and in antiphase

A

same amplitude and in antiphase

pg 32

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13
Q

patterns of stationary wave that can be observed

both walls are up

draw and state the f, lamda and v

A

pg 33

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14
Q

formation of stationary wave in string

A
  1. wave reflected at the end
  2. the reflected and incident waves with same frequency, about the same amplitude and travelled in opposite direction
  3. waves superpose and form stationary wave
  4. at antinodes, 2 in phase waves superpose. constructive interference occurs and amplitude of resultant wave is max
  5. at nodes, 2 antiphase waves superpose. destructive interference occurs and amplitude of resultant wave is zero
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15
Q

stationary wave on spring

speed depends on

A

tension and mass per unit length

if both constant wave speed is constant

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16
Q

stationary wave on spring

f0 is the fundamental frequency

A

2f0, 3f0 , 4f0 are harmonics

2f0 is the second harmonic and give two loops

17
Q

stationary wave on string

water droplets form at

A

nodes no net movement at these points

18
Q

stationary on

cello/guitar
cantilever
microwave
microwave oven

A

pg 33 , 34 , 35

19
Q

stationary wave
- sound waves

closed pipes

find lamda and frequency

A

pg 36

pink note book

20
Q

stationary wave
- sound waves

open pipe

A

pg 37

pink note book

21
Q

stationary wave
- sound waves

measure frequency
wavelength
speed of sound

A

pg 38

22
Q

stationary wave
- sound waves

explain why minima never zero

A

no complete cancellation

waves have diff amplitude
-amplitude decreases with distance / energy loss due to reflection

23
Q

stationary wave
- sound waves

as microphone is moved towards the metal plate the amplitudes at the minima gradually decreases

why

A

as the microphone moves towards the plate

the path diff decreases

amplitude of waves get smaller

24
Q

compare stationary and progressive wave

first 2

A

P

  1. energy is transferred along the direction of propagation
  2. the wave profile moves in the direction of propagation

S

  1. no energy is transferred along the direction of propagation ( stored energy )
  2. the wave profile does not move in the direction of propagation
25
Q

q on pg 40

A

pg 40

26
Q

displacement vs distance with time

t=0
t=1/4 T
t=1/2 T
t=3/4 t
t=T
A

pg 41

27
Q

stationary wave on cello or guitar string

explain what happens

A
  1. bow alternately pulls and release string
    - produce travelling wave
  2. wave reflected at the end
  3. they ( who? )
    - incident and reflected wave move with the same frequency amplitude and speed
  4. they travelled in opposite direction and they superpose to form standing wave
  5. this cause the string to vibrate with greater amplitude
    - the air column next to string vibrate and sound is heard
  6. longer the string, the bigger the volume of air is set to vibrate and louder the sound is heard
  7. damping is greater so sound last for shorter time
28
Q

stationary wave on cello or guitar string

from the working mechanism

give conclusions

A
  1. sound heard is progressive longitudinal wave * NOT STATIONARY WAVE
  2. wave formed on string is transverse stationary wave
    - no energy is transferred along the string no sound is heard
  3. the sound produced consists of more than 1 frequencies of different amplitudes
29
Q

microwave to produce stationary wave

plan

A

what ya need: microwave detector attached to CRO and transmitter, metal plate

  1. moves microwave detector along the direction of motion of wave ( go forward and backward in front of transmitter )
  2. mark the 1st and 11th node
  3. measures the distance bwtn 1st and 11th node
  4. calculate wavelength using formula pg 34 / 35
30
Q

microwave to produce stationary wave

explain why maxima and minima detected btwn transmitter and metal plate

A
  1. waves reflected from metal plate
  2. the reflected and incident waves share the same frequency, amplitude and speed
  3. they move in opposite direction and superpose to form standing wave
  4. maxima at antinodes, in phase waves superpose to form constructive interference ( nope : resultant wave has maximum amplitude )
  5. minima at nodes, anti phase superpose to form destructive interference

( resultant wave has zero amplitude )= never write this for formation of standing wave cause minima never zero incomplete cancellation, amplitude changes

31
Q

microwave oven creating standing waves

A

the microwave source within the oven emits coherent waves from all directions

the waves are reflected off the walls and they arrived at the same spot by several diff routes

interfere and form standing wave

path diff= n lamda , constructive interference, hot spot in phase

phase diff = ( n + 1/2 lamda ) , destructive interference , cold spot , antiphase

caused uneven heating of food, so we use rotating turntable

32
Q

stationary sound wave

closed pipe

give the conclusion regarding

frequency
when speed is constant
if frequency kept constant, the possible lengths that could form standing wave

A

pg 36

33
Q

stationary sound wave

closed pipe

if fine dust is sprinkled along its length, at certain length the dust forms small heaps in the tube

why

A

at antinodes there are no heaps
- wave has max amplitude of vibration

at nodes, there are no heaps
- amplitude of vibration is zero

dust is pushed to nodes

34
Q

compare stationary and progressive wave

next 2

A

P

  1. every point along the direction of propagation is displaced but at different instants
  2. every point has the same amplitude ( all have max / have a chance to go max )

S

  1. there are points known as nodes where no displacement occurs
  2. ppints btwn 2 successive nodes have diff amplitudes ( only antinodes points have max amplitude )
35
Q

compare stationary and progressive wave

last 1

A

P
5. neighbouring points are not in phase

S
5. all points btwn 2 successive nodes vibrate in phase with each other

Physics (12 decks)

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