The type of electromagnetic wave that can span longer than a mountain range is a radio wave.

Quick Scoop

Radio waves sit at the low-frequency, long-wavelength end of the electromagnetic spectrum.

Some radio wavelengths can be many kilometers long, which easily exceeds the width of most mountain ranges.

Tiny example to picture it

Imagine a radio wave whose wavelength is about 10 km; that single “crest‑to‑crest” distance already stretches farther than many individual mountains and can rival or exceed the span of an entire mountain range.