Amplitude, wavelength and frequency
Amplitude is the wave's maximum displacement from rest. Wavelength is the distance between matching points on neighbouring waves, in metres. Frequency is the number of waves per second, in hertz (Hz).
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Analogy
On a swing: how high you go is amplitude, and how many swings per minute is frequency.
Example
10 waves pass a point in 5 s.frequency = 10 / 5 = 2 Hzperiod = 1 / 2 = 0.5 s
In practice
A louder sound has a larger amplitude. A higher note has a higher frequency.
Practice
Flashcards
- What is frequency and its unit?The number of waves per second, in hertz (Hz).
Interview questions
- A water wave has a frequency of 4 Hz and a wavelength of 0.5 m. Calculate its speed and say how far it travels in 10 s.
- v = f x wavelength = 4 x 0.5 = 2 m/s
- Distance = speed x time = 2 x 10
- Distance = 20 m
Questions people ask
What is the difference between amplitude and frequency?
Amplitude is how big the wave is, measured from the middle to a peak. Frequency is how many complete waves go past a point each second. Turning up the volume increases amplitude. Playing a higher note increases frequency. They are independent: you can change one without the other.
What is the unit of frequency?
The hertz (Hz). One hertz means one complete wave each second. Larger values use kilohertz (kHz, 1,000 Hz) or megahertz (MHz, 1,000,000 Hz). A radio station at 100 MHz sends out one hundred million waves every second. Radio and light waves have far larger values.