Which electromagnetic wave has the longest wavelength among these options?

Which electromagnetic wave has the longest wavelength among these options?

• A. Microwave
• B. Ultraviolet light
• C. Radio
• D. X-rays

Answer: (C)

Wavelength and frequency are inversely related for electromagnetic waves traveling in the same medium, so a longer wavelength means a lower frequency. Among these options, radio waves have the lowest frequency, which gives them the longest wavelength. Radio waves span from about millimeters up to thousands of kilometers, far longer than microwaves (which are about centimeters to meters) and ultraviolet and X-rays (which have much shorter wavelengths, from tens of nanometers down to picometers).