The Doppler Effect Flashcards
1
Q
Caps Lock
A
2
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Verr. Maj.
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3
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Ctri
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4
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Away tens lower frequency
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5
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Closer = higner frequen
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6
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nese ar
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7
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•aveling
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8
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A pound up
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9
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a)
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10
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The Doppler Effect:
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11
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Wave sading
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12
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towards
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13
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= f
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14
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Vw
A
15
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‡ Vo
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16
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Vu F
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17
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Vs
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18
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volucity of Gosayer
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19
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volocity of Source.
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20
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rees
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21
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f→ is the new fraung
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22
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experienced ty
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observer.
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Q
- → is the origiNa
A
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trequency of the source
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Otiginal
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Vi → is the speed of
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the wave.
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V. → is the speed of
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The observer.
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Vs→ is the speed of the source.
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* USe + oN top t - oN bottom if
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They are moving TOwARDs each other
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* USe - oN top & + oN boton if
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They are moving AWAY from each other.
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Ex:
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A car horn sounds at 1200 Hz. Assuming the speed of sound is
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345 m/s
what new frequency will we hear if:
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a) the car travels toward us at 25 m/s
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b) the car travels away from us at 25 m/s
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+ Vo
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b) f = 1200(345 + 25)
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Vs
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= 1200 / 3.
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10)
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345
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+
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= 1200 / 345
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-
50
25
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= 1200(09324324132)
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345
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= 1200 / 320
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= 1200(1.015125)
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= 1118 Hz
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= 1294 Hz
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wt
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r
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= 1200/345 + 2
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- 345- 0
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TRY THIS:
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= 1300(349)
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= 1200/0.407368
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ANSWER:
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€ 1297 Hz
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Therefore
as a car passes us we hear a total doppler shift of:
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Total Shift = (1294 - 1119) = 175 Hz
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Now recalculate the above shifts if the source is
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stationary and its the observer that is moving!
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a) 1287 Hz
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b) 1113 Hz
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Text Assignment: p.409
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# 7 - 10
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1) - (13 - 20)
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=1200/343 -
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345 7 0
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= 1200(320
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345
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= 1200/0.02755
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= 1113Hc
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e aron a-.
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Lundon
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Doppler Effect
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If we assume that the original frequency of both sources dipping
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into the water was 2.0 Hz
let's take a look at how an outside
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observer (ducky) will experience the waves:
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Opject that's making = Source
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the wave
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Ducky bobs up & down
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at 2.0 Hz.
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Ducky bobs up & down
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at 2.0 Hz.
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S1 - stationary source
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The observer experiences the waves at the same frequency they
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were created if both the source and the ducky are stationary!
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Ducky bobs up & down
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less frequent than
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2.0 Hz.
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Ducky bobs up & down
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more frequent than
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2.0 Hz.
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S2 - source moving while
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making waves
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The observer experiences the waves at a different frequency than
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were created! If the source/ducky move towards each other the
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frequency will increase! If the source/ducky move away from each
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other the frequency will decrease!
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WORK!
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These are a series of pictures of the source of the circular waves
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traveling faster and faster...
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V. Wi
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B
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V = Vw
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Vs
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mand is moving
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Faster
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E
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Souvee is the
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Same as the wanes
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SinG: Vui
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Vp
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Vp = Va
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Sine
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Janic
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Vs
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> > Vw
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boom
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The objects (sources) in A & B are moving at "subsonic" speeds
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which means slower than the speed of sound. You can see the
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doppler shift happening the faster it goes. Object C is moving at
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the speed of sound. Objects D & E are moving "supersonic" which
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means faster than the speed of sound. In those cases you can see a
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"wake" developing to either side of the path (see below in green).
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When the wake hits the
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observer she will hear a
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sonic BOOM!
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A sonic boom can be heard as the wake passes by the ear of an
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observer standing beside the path of the object. Usually
this is a
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jet plane because other vehicles don't travel that fast... unless you
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put a jet engine on a car and then
well
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Things that travel as fast as sound we say they are traveling at
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MACH 1.0
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peed of sound
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Double the speed of sound they are said to be traveling at
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MACH 2.0
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speed of sound
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345 m/s -
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345 m/s
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345 m/s
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345 m/s -
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MACH
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— 1.0
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-- 2.
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0.8
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-1.4
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actual speed
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345 m/s
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- 690 m/s
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276 m/s
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483 m/s
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MACH =
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345
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If this stuff is still confusing
then check out these 2 links for
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help:
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1. https://www.youtube.com/watch?v=dc717Qqa8xk
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2. https://www.youtube.com/watch?v=G38uOhJQY7U
