The wave equation c = f x lambda explained
What the speed, frequency and wavelength of a wave mean, why they trade off, and how photon energy follows from frequency.
Three quantities, one equation
Every travelling wave links three numbers: its speed c, its frequency f and its wavelength lambda. Frequency counts how many crests pass a fixed point each second, measured in hertz, while wavelength is the distance between neighbouring crests. Multiply how often a crest arrives by the spacing between crests and you get how fast the pattern moves, which is exactly c = f x lambda. Knowing any two of the three fixes the third.
Why frequency and wavelength trade off
For light in a vacuum the speed is fixed at 299,792,458 metres per second, so frequency and wavelength must move in opposite directions to keep their product constant. Double the frequency and the wavelength halves. That is why gamma rays with enormous frequencies have tiny wavelengths, while long radio waves oscillate slowly. Entering 100 MHz here yields about 3 metres, and shrinking the wavelength to 500 nanometres pushes the frequency into the hundreds of terahertz.
From frequency to photon energy
Light also behaves as a stream of photons, and each photon carries an energy set only by frequency through E = h x f, where h is the Planck constant. Higher frequency light delivers more energetic photons, which is why ultraviolet and X-rays can break chemical bonds while radio waves cannot. This tool computes that energy in joules alongside the conversion, so a single input gives you the wavelength, the frequency and the per-photon energy together.
Reading the spectrum
The same equation spans the whole electromagnetic spectrum, from kilometre-long radio waves to picometre gamma rays. Radio and microwave bands are usually quoted in megahertz or gigahertz, visible light in nanometres of wavelength, and high-energy radiation by photon energy. Being able to jump between these descriptions is useful whenever a datasheet uses one convention and your problem needs another, which is the everyday job this converter handles.