The speed of all electromagnetic waves in a vacuum is the same. This speed is approximately 299,792,458 meters per second, often rounded to 3 x 10^8 m/s, which is also known as the speed of light.

What changes across the electromagnetic spectrum is the frequency and wavelength of the waves:

* Frequency: The number of wave cycles that pass a point per second (measured in Hertz, Hz).

* Wavelength: The distance between two corresponding points on adjacent waves (measured in meters, m).

The relationship is this:

* Higher frequency = Shorter wavelength

* Lower frequency = Longer wavelength

So, while the speed of the waves remains constant, their frequency and wavelength vary, which affects their energy and how they interact with matter.

Example:

* Radio waves: Have very long wavelengths and low frequencies.

* Gamma rays: Have very short wavelengths and high frequencies.

Let me know if you have more questions about the electromagnetic spectrum!