The Electromagnetic Spectrum: Waves, Uses & Hazards (MYP Physics)
Radio, light, X-rays and gamma rays look nothing alike in everyday life, yet they are all the same kind of wave — electromagnetic waves — differing only in wavelength and frequency. Understanding the spectrum as one family, ordered by energy, makes their very different uses and dangers easy to organise.
Try it yourself: four zones covering knowledge, investigation, calculation and impact, each mapped to an MYP criterion.
The seven regions, in order
From longest wavelength (lowest energy) to shortest wavelength (highest energy):
- •Radio waves — broadcasting and communication.
- •Microwaves — cooking, mobile and satellite signals.
- •Infrared — remote controls, thermal cameras, heating.
- •Visible light — the only part we can see, roughly 400–700 nm.
- •Ultraviolet — sterilising, and the cause of sunburn.
- •X-rays — medical imaging.
- •Gamma rays — sterilising equipment and treating cancer.
What they all share
All electromagnetic waves are transverse, can travel through a vacuum, and travel at the same speed there: about 3.00 × 10⁸ m/s. They differ in wavelength and frequency, linked by the wave equation speed = frequency × wavelength (c = fλ). Because c is fixed, higher frequency always means shorter wavelength.
Energy and hazards
Energy increases with frequency, so the high-frequency end is the most hazardous. Ultraviolet, X-rays and gamma rays can ionise atoms and damage living cells, which is why sunscreen, lead shielding and limited X-ray exposure matter. Lower-frequency waves such as radio carry too little energy per photon to ionise atoms.
Applying it in an assessment
Typical questions ask you to match a wave to a use and explain why its properties suit it — for example, why X-rays pass through soft tissue but are absorbed by bone. Then link the same property to the hazard, and weigh benefit against risk for Criterion D.
Frequently asked questions
Radio, microwave, infrared, visible light, ultraviolet, X-ray, gamma — from longest wavelength to shortest.
Yes, in a vacuum they all travel at about 3.00 × 10⁸ m/s.
They have much higher frequency and energy, enough to ionise atoms and damage cells, whereas radio waves carry too little energy per photon.