Here are the formulas, in case you feel like putting them in your notebook.
Actually, this is only ONE formula, and you should memorize this one:
Speed = (frequency) x (wavelength) .
With just a pinch of algebra, the others come straight from that one.
So if you memorize that one, you can whip these up any time you
need them:
Frequency = (speed) / (wavelength)
and
Wavelength = (speed) / (frequency) .
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Using a formula:
Wavelength = (speed) / (frequency) .
= (10 m/s) / (5 / 2 sec)
= ( 10 ยท 2 / 5 ) (m-sec/s)
= 4 meters .
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Using your brain:
5 students in a parade march past a light pole in 2 seconds.
They're all marching at 10 m/s.
How far apart are they ?
-- If 5 march past in 2 seconds, then 2.5 march past every second.
-- 2.5 march past in the time it takes them to move 10 meters.
-- So 2.5 of them stretch 10 meters.
-- The distance from one to the next is (10) / (2.5) = 4 meters .