Which one of the following represents the correct order for the wavelengths of different waves ?

The electromagnetic spectrum is ordered by wavelength (λ) or frequency (f). Wavelength is inversely proportional to frequency (c = fλ). Radio waves have the longest wavelengths in the spectrum, followed by microwaves, infrared, and visible light.

Within the radio frequency range:

• AM Radio (Amplitude Modulation): Operates at lower frequencies (approx. 540–1600 kHz), resulting in longer wavelengths, typically ranging from 187 to 555 meters.
• FM Radio (Frequency Modulation): Operates at higher frequencies (approx. 88–108 MHz), resulting in shorter wavelengths, typically around 2.7 to 3.4 meters.

Microwaves have wavelengths ranging from 1 mm to 1 meter, which are shorter than FM waves. Infrared radiation (700 nm to 1 mm) and Visible light (400 nm to 700 nm) follow with progressively shorter wavelengths. Therefore, the correct descending order is AM radio > FM radio > Microwaves > Infrared > Visible light.