Electromagnetic Waves
Changing electric and magnetic fields propagate as waves.
About this topic
Maxwell showed that changing electric and magnetic fields sustain each other, producing self-propagating transverse waves that travel at c = 1/√(μ₀ε₀), the speed of light. The fields oscillate at right angles to each other and to the direction of travel.
Hertz generated radio waves in 1887, confirming the theory. They carry energy and momentum, need no medium and span the spectrum from radio to gamma rays, in order of increasing frequency: radio, microwave, infrared, visible, ultraviolet, X-ray and gamma. All travel at 3 × 10⁸ m/s in a vacuum, with v = fλ linking speed, frequency and wavelength.
They are the basis of wireless communication, from radio and Wi-Fi to mobile phones, while microwaves cook food, X-rays image bones and infrared cameras see heat. Sunlight reaching Earth is a stream of such waves.
A misconception is that radio waves are sound waves. They are electromagnetic and silent until a receiver converts them. Higher frequency waves carry more energy per photon, which is why ultraviolet and X-rays are more harmful than radio waves.
Key ideas
- Maxwell predicted them
- Travel at light speed
- Radio, light and X-rays
Quick check
Use cases: where Electromagnetic Waves helps
- Homework: review the key idea behind Electromagnetic Waves before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Electromagnetic Waves without notes.
- Visual learning: play with the interactive lab to see how Electromagnetic Waves changes when you adjust its inputs.
- Teaching a friend: explain Electromagnetic Waves in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Electromagnetic Waves?
Changing electric and magnetic fields propagate as waves.
What will I learn in Electromagnetic Waves?
Maxwell predicted them. Travel at light speed. Radio, light and X-rays.
Is Electromagnetic Waves part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Electromagnetic Waves lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Electromagnetic Waves?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.