[Radiologic Physics] Ep 4 – Electromagnetic Energy

This episode provides a focused examination of electromagnetic energy and its properties as they apply to radiologic science. Radiation is defined broadly before narrowing to electromagnetic energy — its photon-based composition, massless and chargeless nature, sinusoidal travel at the speed of light, and three fundamental wave properties: wavelength, frequency, and amplitude. The inverse relationship between wavelength and frequency is established through the wave equation (c = λ × f), with a worked numerical example, and Planck's equation (E = hν) is introduced to connect photon energy directly to frequency. The electromagnetic spectrum is then surveyed from radio waves through microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, with each type characterized by its relative wavelength, frequency, and energy. Visible light's wavelength range (400–700 nm) and the ROYGBIV color sequence are covered, along with the clinical note that the human eye peaks at 550 nm. Sound waves are identified as the key exception — non-electromagnetic, requiring matter to travel, and forming the basis of diagnostic ultrasound. The episode closes by connecting specific spectrum regions to radiology: X-rays for radiograph production, visible light for image viewing, and radio waves for MRI. Content is structured to support radiologic technology programs preparing for imaging coursework and ARRT certification review. This episode aligns with the Safety content category — Radiation Physics and Radiobiology subcategory — of the ARRT Radiography Examination Content Specifications. Audio content is adapted from original instructional material developed by Professor Sanjay Arya, M.S., R.T.(R)(MR) for radiologic technology education. Part of the Radiologic Physics series — Quantum Imaging Lab. © 2026 Quantum Imaging Lab. All rights reserved.