What is the practical reason to give the name “electromagnetic waves”?

Question

I am a teacher in mathematics. I know an interpretation for solutions of Maxwell equations as simultaneous perpendicular oscillations of electric field and magnetic field, and I know that they need not become radiation or propagation. This provides a theoretical reason for the name “electromagnetic waves” for radiated energy waves, which have the speed in vacuum that coincides with the speed of light in vacuum.

The electromagnetic waves, for which wavelengths are (approximately) between 1 mm to 1m, are generally called microwaves. The energy waves obtained by shooting electrons in micro ovens are also called micro waves, for which the speed in vacuum is less than the speed of light in vacuum, in view of de Broglie law. Since micro waves of micro ovens have less speed, my first question is the following:
(1) Why should we call this type of micro waves as electromagnetic waves?

I noted that there is no device to practically observe both electric field component and magnetic field component separately for an electromagnetic wave such that both components have same common wavelength. I like to give a stress for the phrase “common wavelength”.
Microwaves corresponding to the ones generated in micro ovens may lose electrons when there is an arrangement to observe electrons, and one may claim that electric field component has been separated. I am particular about “common wavelength”.
Since there is no practical existence of two components for other types of electromagnetic waves, with common wavelength, my second question is the following:
(2) Why should we call the other types of waves as electromagnetic waves?

My common question is the following:
What is the practical reason to give the name “electromagnetic waves”?

P.S. One site to call rays in micro ovens is: https://www.mathsisfun.com/physics/waves-radio-microwave.html#:~:text=Microwave%20ovens%20use%20electromagnetic%20waves,vibrate%20fast%20and%20heat%20up.
Some electromagnetics waves (also called micro waves) having wavelength between 1mm and 1m may have the speed in vacuum as c, the speed of light in vacuum.

Answer 1

The energy waves obtained by shooting electrons in micro ovens are also called micro waves

Do you have a reference for this? There are electrons accelerated inside the magnetron, but they are not called microwaves and they are not shot from the device. Instead it is the radiation from the accelerated electrons that is called microwave.

for which the speed in vacuum is less than the speed of light in vacuum

No. The microwaves that are emitted from the magnetron into the oven chamber are EM waves, not matter. They like all other EM waves propagate at the same speed in a vacuum.

Answer 2

Microwaves, radio waves, infrared (waves), ultra-violet (waves), visible light, X-rays/Röntgen waves, gamma-rays are all the names for different parts of the electromagnetic spectrum, i.e. for electromagnetic waves of different frequencies.

The reason for calling them differently is because they usually have different properties in terms of

• how we percieve them
• how (and whether) they propagate
• how they are generated
• the historical use and discovery, which is typically teh consequence of the above listed factors.

Electrons are typiclaly involved in generation of electromagnetic waves and the OP seems to confuse the method of generating the microwaves with the waves themselves (which are electromagnetic waves with no electrons).