Understanding Wave Frequency Calculation from Graphs

Determining wave frequency from a graph

f • Frequency = #of cycles/time • Measured in Hertz (Hz)

1 cycle = 1 full wave to repeat itself

3 cycles 2 4 5 6 7 8 9 10 11 12 1 3 Time in seconds

from 0 to 12 seconds 0 2 4 5 6 7 8 9 10 11 12 1 3 Time in seconds

f=3/12 s = ¼ Hz 2 4 5 6 7 8 9 10 11 12 1 3 Time in seconds

Or determine the time for 1 full wave cycle

1 cycle in 4 seconds= ¼ Hz 0 2 4 5 6 7 8 9 10 11 12 1 3 Time in seconds

Period symbol T • The time for 1 cycle

The period for 1 wave is 4 seconds T=4 2 4 5 6 7 8 9 10 11 12 1 3 Time in seconds

What is the frequency? 8 10 14 20 22 24 0 2 4 6 12 16 18 Time in seconds

? 0 to 24 seconds 3 cycles 8 10 14 20 22 24 0 2 4 6 12 16 18 Time in seconds

3/24 s= 1/8 Hz 0 to 24 seconds 3 cycles 8 10 14 20 22 24 0 2 4 6 12 16 18 Time in seconds

OR • Frequency – 1 cycle in x seconds

f=1 cycle in 8 seconds= 1/8 Hz 8 10 14 20 22 24 0 2 4 6 12 16 18 Time in seconds

Quiz yourself

On a piece of paper number 1 through 3 and determine the frequency of the following waves.

#1 f= ? 6 7 8 9 10 0 1 2 3 4 5 11 12 Time seconds

#2 f= ? 18 20 22 22 24 0 2 6 8 10 12 14 16 26 4 Time seconds

#3 f = ? 40 45 50 55 5 20 25 30 35 60 65 70 0 10 15 Time seconds

Check your answers Check your answers

#1 f= 1/8 Hz 6 7 8 9 10 0 1 2 3 4 5 11 12 Time seconds

#2 f= 1/8 Hz 18 20 22 22 24 0 2 6 8 10 12 14 16 26 4 Time seconds

#3 f = 1/20 Hz 40 45 50 55 5 20 25 30 35 60 65 70 0 10 15 Time seconds

How did you do?

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