Which of the following electromagnetic waves has the highest frequency?

Analyze the question: You're asked which of the listed electromagnetic waves has the highest frequency.

Explain the concept: All electromagnetic waves travel at the speed of light (c = 3 × 10⁸ m/s) in a vacuum. They are related by:

c = fλ, so f = c/λ

This means frequency and wavelength are inversely related: the shorter the wavelength, the higher the frequency. Frequency is also directly proportional to photon energy (E = hf).

The electromagnetic spectrum (lowest to highest frequency):

Radio waves → Microwaves → Infrared → Visible light → Ultraviolet → X-rays → Gamma rays

Solution: Let's place the options on the spectrum:

• B. Radio waves: lowest frequency of the four
• D. Infrared rays: higher than radio waves
• A. Ultraviolet rays: higher than infrared
• C. X-rays: higher than ultraviolet

X-rays have the shortest wavelength (about 10⁻⁸ to 10⁻¹¹ m) and therefore the highest frequency among the options given.

Answer: C. X-rays

Exam tip: Use the memory phrase "Righteous Men In Vegas Understand X-rated Games" to remember the order: Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma. Frequency increases as you move left to right. For "highest frequency" questions, pick the option furthest to the right. Gamma rays would win if they were listed, but here X-rays are the furthest right.