How is the speed of an electromagnetic wave calculated from wavelength and frequency?

The speed of an electromagnetic wave is calculated by finding the product of its wavelength and its frequency.1

In physics, this relationship is expressed by the formula:
$$v=\lambda f$$

Where:
* $v$ is the velocity (or speed) of the wave.
* $\lambda$ (the Greek letter lambda) represents the wavelength, which is the distance between consecutive wave crests.2
* $f$ represents the frequency, which is the number of cycles the wave completes per second, measured in hertz.2

Alternatively, if the speed of the wave ($c$) is known, the frequency can be determined by dividing the speed by the wavelength: $f=c/\lambda$. In a vacuum, electromagnetic waves propagate at a constant speed of light, which is defined as exactly 299,792,458 metres per second.234