Determining wave frequency from a graph

f

• Frequency = #of cycles/time

• Measured in Hertz (Hz)

• 1 cycle = 1 full wave to repeat itself

3 1 2 4 5 6 7 8 9 10 11 12

Time in seconds

3 cycles

from 0 to 12 seconds

3 1 2 4 5 6 7 8 9 10 11 12

Time in seconds

0

f=3 /12 s = ¼ Hz

3 1 2 4 5 6 7 8 9 10 11 12

Time in seconds

• Or determine the time for 1 full wave cycle

1 cycle in 4 seconds= ¼ Hz

3 1 2 5 6 7 8 9 10 11 12

Time in seconds

0 4

• Period symbol T

• The time for 1 cycle

The period for 1 wave is 4 seconds T=4

3 1 2 4 5 6 7 8 9 10 11 12

Time in seconds

What is the frequency?

0 2 4 6 8 10 12 14 16 18 20

Time in seconds

22 24

?

0 2 4 6 8 10 12 14 16 18 20

Time in seconds

22 24

3 cycles 0 to 24 seconds

0 2 4 6 8 10 12 14 16 18 20

Time in seconds

22 24

3 cycles 0 to 24 seconds3/24 s= 1/8 Hz

OR

• Frequency – 1 cycle in x seconds

f=1 cycle in 8 seconds= 1/8 Hz

0 2 4 6 8 10 12 14 16 18 20

Time in seconds

22 24

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

#1 f= ?

0 1 2 3 4 5 6 7 8 9 10 11 12

Time seconds

#2 f= ?

Time seconds

0 2 4 6 8 10 12 14 16 18 20 22 22 24 26

#3 f = ?

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Time seconds

• Check your answers

#1 f= 1/8 Hz

0 1 2 3 4 5 6 7 9 10 11 12

Time seconds

8

#2 f= 1/8 Hz

Time seconds

0 2 4 6 10 12 14 16 18 20 22 22 24 268

#3 f = 1/20 Hz

0 5 10 15 25 30 35 40 45 50 55 60 65 70

Time seconds

20