Answer:
wavelength
Step-by-step explanation:
An electromagnetic waves is produced due to interaction of oscillating electric and magnetic field when they interacts perpendicular to each other. For example, Gamma rays, X rays , ultraviolet rays, visible radiations, infrared rays, micro waves, radio waves.
All the electromagnetic waves have velocity equal to velocity of light.
If the frequency of electromagnetic wave is unknown then we find the wavelength of wave. the formula used is
Wave speed = wavelength x frequency