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A. Phase

"In Phase" (0°) – points on a single periodic wave that have the same displacement (from equilibrium  position) and moving in the same direction

Whole number of wavelengths apart

A & ____ A & ____  B & ___ B & ___

A & E, A & I, A & M

B & F, B & J, B & N

"Out of Phase"– (180⁰)

- same displacement from equilibrium position but going in a different direction

½, 1½, 2½ etc wavelengths apart

A & C, B & D, F & H 

Which 2 points are in phase?

C and F

 2 points that are 180°
 out of phase?

B and D

E and G

A and F

(A and C are less than 180 degrees out of phase)

B. Wavelength – distance between two consecutive points in phase

Wavelength - St. Mary's Physics Online

    - determined by medium

λ = lambda

- length of one cycle #m/cycle

Ex) Wavelength?

June 2000

λ = 5.0 m/2.5 cycles 

λ = 2.0 m 

Amplitude? Wavelength?

Amplitude = .10 m

Wavelength = .60 m

Jan 2004

Amplitude A?,  B?,  C?

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

1.  V = fλ    solve for f: 

inverse relationship f = v/λ

2. Speed of a wave depends on the medium
(waves move slower in dense media)

Speed Of a Mechanical Wave - Monterey Institute

Ex) The periodic wave in the diagram below has a frequency of 40. hertz. What is the speed of the wave?

What is the speed of the wave?

(1) 13 m/s (2) 27m/s

(3)60. m/s (4) 120m/s

Jan 2002 Test

V = fλ

V = 40. Hz(1.5 m)

(3)60. m/s

3. Velocity sound = 3.3 x 10² m/s

(Air, Reference Table, room temperature)

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?

About 1 million times

When do you see lightning and hear thunder almost simultaneously?

When lightning is close

Large gap between when you see lightning and hear thunder?

Lightning is far away

Did you know ...

'...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.'

- Ask Yahoo

Wave Behavior