Do electromagnetic waves exist outside the electromagnetic spectrum?

The term 'electromagnetic spectrum' describes the set of frequencies at which electromagnetic waves can exist. The concept of an electromagnetic wave being "outside" the electromagnetic spectrum is utterly nonsensical due to the definition of the latter.

Does any electromagnetic radiation exist which has wavelength more than 100 kilometers?

Yes. They're designated as the Extremely Low Frequency band.

Where does that band end, you ask? nowhere. Electromagnetic waves can exist, as far as known physics can tell. There is a point at which the period of the wave is longer than a human lifetime, so we, as finite beings, will never observe such waves; also, there are practical concerns in that waves below the usual ELF band, i.e. with frequencies below 3Hz and wavelengths longer than 100,000 km, really don't couple very well with human-made devices that tend to be shorter than 100,000 km. However, both of those objections are unimportant ─ there's nothing in known physics that says that should waves should not exist, even at arbitrarily low frequencies.

Do electromagnetic waves exist outside the electromagnetic spectrum?

The term 'electromagnetic spectrum' describes the set of frequencies at which electromagnetic waves can exist. The concept of an electromagnetic wave being "outside" the electromagnetic spectrum is utterly nonsensical due to the definition of the latter.

Does any electromagnetic radiation exist which has wavelength more than 100 kilometers?

Yes. They're designated as the Extremely Low Frequency band.

Where does that band end, you ask? nowhere. Electromagnetic waves can exist, as far as known physics can tell. There is a point at which the period of the wave is longer than a human lifetime, so we, as finite beings, will never observe such waves; also, there are practical concerns in that waves below the usual ELF band, i.e. with frequencies below 3Hz and wavelengths longer than 100,000 km, really don't couple very well with human-made devices that tend to be shorter than 100,000 km. However, both of those objections are unimportant ─ there's nothing in known physics that says that should waves should not exist, even at arbitrarily low frequencies.

And, for completeness: no, there isn't any high-frequency limit, either. When you go through the infrared and visible and into the UV range, the wave's frequency $f$ cedes some of its importance to the corresponding photon energy $E=hf$, and you need to use quantum mechanics to understand the implications of a wave being at a certain frequency, but nothing changes about the allowed frequencies.

As far as the ultimate limits, go, we know that at some point at extremely high photon energies, at the latest at the Planck scale, the physics we know is no longer a good description, and the description must shift over to other (as yet unknown) laws. It may well be that no photon with energy higher than the Planck energy is possible, but we really don't know.

Do electromagnetic waves exist outside the electromagnetic spectrum?

The term 'electromagnetic spectrum' describes the set of frequencies at which electromagnetic waves can exist. The concept of an electromagnetic wave being "outside" the electromagnetic spectrum is utterly nonsensical due to the definition of the latter.

Do electromagnetic waves exist outside the electromagnetic spectrum?

The term 'electromagnetic spectrum' describes the set of frequencies at which electromagnetic waves can exist. The concept of an electromagnetic wave being "outside" the electromagnetic spectrum is utterly nonsensical due to the definition of the latter.

Does any electromagnetic radiation exist which has wavelength more than 100 kilometers?

Yes. They're designated as the Extremely Low Frequency band.

Where does that band end, you ask? nowhere. Electromagnetic waves can exist, as far as known physics can tell. There is a point at which the period of the wave is longer than a human lifetime, so we, as finite beings, will never observe such waves; also, there are practical concerns in that waves below the usual ELF band, i.e. with frequencies below 3Hz and wavelengths longer than 100,000 km, really don't couple very well with human-made devices that tend to be shorter than 100,000 km. However, both of those objections are unimportant ─ there's nothing in known physics that says that should waves should not exist, even at arbitrarily low frequencies.