The product of frequency and wavelength being equal to the velocity of light is a fundamental relationship known as the wave equation or the equation of wave propagation. It applies to any type of wave, including electromagnetic waves like light.
The equation is stated as:
velocity = frequency × wavelength
In the case of light, it specifically refers to the speed of light in a vacuum, denoted by the symbol "c." The equation can be written as:
c = f × λ
Where: c is the speed of light in a vacuum (approximately 299,792,458 meters per second), f is the frequency of the light wave (measured in hertz, which represents the number of cycles per second), λ is the wavelength of the light wave (measured in meters).
This relationship arises from the wave nature of light. Light is an electromagnetic wave that consists of oscillating electric and magnetic fields. The frequency of light corresponds to the number of wave cycles passing through a point in one second, while the wavelength represents the spatial length of one complete wave cycle.
The product of frequency and wavelength being equal to the speed of light is a consequence of the wave's propagation speed. In a medium such as a vacuum or air, electromagnetic waves, including light, travel at a constant speed. This relationship holds true for all electromagnetic waves, not just visible light, and is a fundamental property of these waves in our universe.