which electromagnetic waves has the longest wavelength

The electromagnetic waves with the longest wavelength in the spectrum are radio waves, specifically the very low frequency (VLF), ultra low frequency (ULF), and extremely low frequency (ELF) radio bands.

Quick Scoop: Direct Answer

• In a standard school/college electromagnetic spectrum:
  • Radio waves have the longest wavelength.

• At the very low-frequency end:
  • ELF/ULF radio waves can have wavelengths of thousands to millions of meters , and in principle there is no strict upper limit.

So if your question is in the usual MCQ/textbook sense (“Which electromagnetic waves has the longest wavelength?”), the correct one-word answer is: radio waves.

Tiny bit of context (in plain language)

Electromagnetic waves all travel at the speed of light in vacuum, and their wavelength λ\lambda λ and frequency fff are related by c=fλc=f\lambda c=fλ.

That means:

• Lower frequency ⇒ longer wavelength.
• Highest frequencies (gamma rays) ⇒ shortest wavelengths.
• Lowest frequencies (radio, especially ELF/ULF) ⇒ longest wavelengths.

In the full spectrum order:

• Radio waves → microwaves → infrared → visible light → ultraviolet → X‑rays → gamma rays, and radio is at the long-wavelength end.

Example you can picture

• A typical FM radio station (~100 MHz) has a wavelength of a few meters.

• ELF or ULF waves used or studied for specialized communication and geophysical phenomena can reach kilometers to much larger scales in wavelength.

TL;DR: Among electromagnetic waves, radio waves have the longest wavelength; at the extreme low-frequency end, their wavelengths can be enormous and, in theory, unbounded.

Information gathered from public forums or data available on the internet and portrayed here.