Speed and Medium for a Wave

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F. Speed – the number of meters a single cycle travels per second

1.  V = fλ

solve for f:

f = v/λ

inverse relationship

2. Speed of wave depends on the medium

(slower in dense media)

Ex) f = 40. hertz. V = ?

(1) 13 m/s (2) 27 m/s (3) 60. m/s (4)120 m/s

Jan 2002 Test

V = fλ

V = 40. Hz(1.5 m)

(3) 60. m/s

Ex) Period = 5.0 sec. V = 20. m/s

Wavelength = ?

V = fλ

Need f????

T = 1/f

5.0 sec = 1/f

f = .20 Hz

V = fλ

20. m/s = (.20 Hz)λ

= 1.0 x 102 m

3. Velocity sound = 3.3 x 102 m/s

(Air, Reference Table, room temperature)

Jet breaking speed of sound
Cambridge U.

 "A "sonic boom" is heard when a plane exceeds the speed of sound. "

sonicboom_hi.mov

Velocity light in a vacuum

= 3 x 108 m/s
(Reference Table)

Wikimedia
Intracloud lightnings over Toulouse (France).
Original source is Image:Lightnings sequence 2.jpg,

About how many times faster is
light

than sound?

p. 1 Reference Table

Gap between time you see lightning and time you hear thunder tells ....

... distance of lightning

If time gap is small?

Lightning is close

Large gap of time?

Lightning far away

Did you know ...

Every 5 seconds gap = 1 mile

'...you can approximate the storm's distance in miles by counting the seconds between the lightning and thunder and dividing by five. It takes about five seconds for the sonic boom to travel one mile, so if you see the sky illuminated by a streak of lightning and count 10 seconds until you hear the low rumble of the thunder, the storm is about two miles away.'

Vibrating Tuning Fork - Slow Motion

Wavelength, frequency,
period, speed, amplitude.

Which 3 are determined by the source of a wave?

frequency, period, amplitude.

 Summary Source Medium frequency speed period wavelength amplitude