Characteristics of Waves
Simple Explanation
Every wave can be described by a few key characteristics: amplitude (the maximum displacement from the rest position, related to the energy carried), wavelength Ξ» (the length of one complete wave cycle), frequency f (how many complete waves pass a point each second, in hertz), and period T (the time for one complete wave, T = 1/f). Wave speed ties these together: v = fΞ».
Why Do We Need It?
These characteristics let you fully describe and compare any wave β from a gentle ripple to a radio signal β using just a few numbers.
Formula
The Wave Speed Equation
v = fΞ»
The speed a wave travels at equals how many complete waves pass a point each second (frequency) multiplied by the length of each wave (wavelength).
- v
- β wave speed, in metres per second (m/s)
- f
- β frequency, in hertz (Hz)
- Ξ»
- β wavelength, in metres (m)
When to use it: Whenever the speed, frequency, or wavelength of a wave needs to be found, given the other two.
Worked Example
Find a wave's speed
A wave has a frequency of 50 Hz and a wavelength of 4 m. Find its speed.
Why Does This Work?
Frequency tells you how many complete wavelengths pass a point every second; multiplying by the length of each of those wavelengths gives exactly the total distance the wave pattern covers each second β which is the definition of wave speed.
Real-Life Example
Radio stations
A radio station broadcasts at a listed frequency, like "98.5 FM."
Since radio waves all travel at the speed of light (a fixed, known speed), knowing the frequency lets you calculate the wavelength (and vice versa) using v = fΞ» β this is exactly how radio receivers are tuned.
Practice
A wave has a wavelength of 2.5 m and travels at 15 m/s. Find its frequency.
MediumA wave has a frequency of 20 Hz. Find its period.
MediumCommon mistake
Confusing frequency and period β a HIGH frequency means a SHORT period (T = 1/f), since more waves passing per second means each individual wave takes less time.
Quick Review
- v = fΞ»; T = 1/f
- Amplitude relates to the energy a wave carries.
- Wavelength is the length of one complete wave cycle.