Wave period and wave speed

The time period of a wave can be calculated using the equation:

Time~period = \frac{1}{frequency}

T = \frac{1}{f}

This is when:

  • the period (T) is measured in seconds (s)
  • frequency (f) is measured in hertz (Hz)

Example

Calculate the time period of a wave with a frequency of 50 Hz.

T = \frac{1}{f}

T = 1 \div 50

T = 0.02~s

Question

Calculate the time period of a wave with a frequency of 400 Hz.

T = 1 \div 400

T = 0.0025~s

Calculating wave speed

The speed of a wave can be calculated using the equation:

wave speed = frequency × wavelength

v = f~\lambda

This is when:

  • wave speed (v) is measured in metres per second (m/s)
  • frequency (f) is measured in Hertz (Hz)
  • wavelength (λ) is measured in metres (m)
Formula triangle demonstrating v equals f times lambda. V at the apex of triangle, f in bottom-left corner and lambda in bottom-right. Also demonstrates f equals v over lambda, lambda equals v over f.

Example

What is the speed of a wave that has a frequency of 50 Hz and a wavelength of 6 m?

v = f \lambda

v = 50 \times 6

v = 300~m/s

Question

What is the speed of a wave with a frequency of 0.2 Hz and a wavelength of 25 m?

v = f \lambda

v = 0.2 \times 25

v = 5~m/s