Question

the waves of the electromagnetic spectrum are separated by
wavelength
amplitude
speed

Explanation:

The electromagnetic spectrum is a range of all types of electromagnetic radiation. Different waves in the spectrum are distinguished by their wavelengths. For example, radio waves have long wavelengths, while gamma rays have very short wavelengths. Amplitude is related to the intensity of the wave (how "strong" it is), not to the separation in the spectrum. All electromagnetic waves travel at the speed of light in a vacuum, so speed does not separate them.

Answer:

wavelength