Calculating wave speed
Wave speed equation
The speed of a wave is related to its The number of waves produced each second. The unit of frequency is hertz (Hz). and The length of a single wave, measured from one wave peak to the next., according to this equation:
\(v = f~ \times \lambda\)
where:
v is the wave speed in metres per second, m/s
f is the frequency in hertz, Hz
λ (lambda) is the wavelength in metres, m
All waves, including sound waves and A transverse wave caused by oscillations in an electromagnetic field., follow this equation. Some particular waves have their own specific speeds.
If you’re studying for the higher tier exam, you will need to be familiar with calculations involving very large and very small numbers by using the ×10x or EXP button on your calculator.
The equation \(\text{speed =}~\frac{\text{distance}}{\text{time}}\) can also be used to calculate the speed of a wave.
Question
Calculate the frequency of ultraviolet radiation.
Its wavelength is 200 × 10-9 (or 200 nm).
Its speed is 3 × 108 m/s.
\(\text{frequency =}~\frac{\text{speed}}{\text{wavelength}}=\frac{{3\times10}^{8}}{{200\times10}^{-9}}={1.5\times10}^{15}{\text{~Hz}}\)