Period T
The period of a wave is the time taken for one wave to be produced or the time for one complete vibration.
It is also the time taken for one wave to pass a point.
Period is a time, and so it is measured in seconds.
Frequency and period
The frequency of a wave can also be calculated using this equation:
\(\text{frequency =}~\frac{\text{1}}{\text{period}}\)
\(\text{f =}~\frac{\text{1}}{\text{T}}\)
where:
f = frequency = number of waves produced by a source per second, in hertz, Hz.
T = period = time it takes for one complete vibration in seconds, s.
Example
A sound wave has a period of 0.0001 seconds.
What is its frequency?
Answer
\(\text{f =}~\frac{\text{1}}{\text{T}}\)
\(\text{f =}~\frac{\text{1}}{\text{0.0001}}\)
f = 10,000 Hz
The frequency of the sound wave is 10,000 Hz.
Question
A radio wave has a frequency of 3 MHz.
What is its period?
\(\text{T =}~\frac{\text{1}}{\text{f}}\)
f = 3 MHz = 3 x 106 Hz
\(\text{T =}~\frac{\text{1}}{\text{3}\times{10}^{6}}\)
T = 0.00000033 s
This can also be written as T = 0.33 x 10-6 = 0.33 渭s
The period of the radio wave is 0.33 渭s.