What does the symbol λ (lambda) represent in electromagnetic theory?

The symbol λ (lambda) in electromagnetic theory represents wavelength. Wavelength is the distance between successive points of a wave that are in phase, such as from crest to crest or trough to trough. It is a crucial parameter in understanding wave phenomena, as it determines the physical properties of electromagnetic waves, including light.

In the context of electromagnetic radiation, the speed of light (c) is related to wavelength (λ) and frequency (f) through the equation c = f * λ. Here, while frequency refers to how many cycles of the wave occur in a second, and period is the time it takes for one cycle to pass a given point, these are distinct concepts from wavelength. Cycle refers to a full waveform, which does not denote a measurement like wavelength does. Therefore, λ specifically denotes the spatial extent of the wave, making it the appropriate symbol for wavelength.