Electromagnetic Radiation Overview

Study Notes

Electromagnetic radiation (EMR) is a ubiquitous phenomenon, taking the form of self-propagating waves in vacuum or matter.
It comprises oscillating electric and magnetic fields, perpendicular to each other and the direction of energy propagation.

EMR is categorized by frequency (or wavelength). Types, in order of increasing frequency and decreasing wavelength, include: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

Radio Waves: Wireless communication (radio, TV, cell phones, Wi-Fi).
Microwaves: Microwave ovens, radar, satellite communication, some wireless technologies.
Infrared Radiation: Night vision devices, remote controls, heat sources in industrial processes.
Visible Light: Human vision, photography, optical communication (fiber optics).
Ultraviolet Radiation: Sterilization, fluorescence, UV curing processes (inks, coatings).
X-rays: Medical imaging (radiography, CT scans), industrial inspection, material analysis.
Gamma Rays: Medical imaging (PET scans), cancer treatment (radiotherapy), industrial material integrity inspection.

A narrow band of frequencies is sensed by the human eye as visible light.
EMR carries energy and momentum, which can be imparted to matter with which it interacts.
EMR is a transverse wave.
EMR travels at the speed of light (approximately 2.998 × 10⁸ m/s).

EMR exhibits both wave-like and particle-like properties (wave-particle duality).
Wave properties manifest in interference and diffraction patterns.
Particle properties mean the particles have distinct positions and momenta (acting as discrete entities).

Amplitude (a): Maximum vertical displacement of a wave cycle.
Wavelength (λ): Distance between two adjacent crests or troughs. Measured in units like Angstroms (Å) or micrometers (µm).
Wave Number: Reciprocal of wavelength, representing the number of waves per unit length (e.g., cm^-1). A higher wave number corresponds to a shorter wavelength.
Frequency (ν): Number of waves passing a point per unit time (e.g., Hz).