# Electromagnetic Spectrum
Confidence: high
Last verified: 2026-05-22
Generation: ai_assisted


## TL;DR

The electromagnetic spectrum encompasses all types of EM radiation, ordered by wavelength/frequency: radio (longest), microwave, infrared, visible light (400-700nm), ultraviolet, X-ray, gamma ray (shortest). All travel at speed of light (c = 299,792,458 m/s). Maxwell's equations (1865) unified electricity, magnetism, and light.

## Core Explanation

Radio waves: communication, broadcasting. Microwaves: radar, cooking, WiFi. Infrared: heat, night vision. Visible: ROYGBIV (red 700nm → violet 400nm). UV: sunburn, vitamin D, sterilization. X-rays: medical imaging, security. Gamma rays: nuclear processes, cancer treatment, most energetic. Photon energy: E = hf (Planck). Higher frequency = higher energy = more penetrating/damaging.

## Further Reading

- [Introduction to Electrodynamics (4th Ed, Griffiths)](https://www.cambridge.org/highereducation/books/introduction-to-electrodynamics/3EDC2A247A70E2F72D685535D315EB68)