Electromagnetic Spectrum
Light is one band of electromagnetic waves ordered by frequency.
About this topic
Visible light is just a narrow slice of the electromagnetic spectrum, which runs in order of increasing frequency: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. All are transverse waves travelling at the speed of light in a vacuum, differing in frequency and wavelength.
Photon energy E = hf rises with frequency, so gamma rays and X-rays are ionising and can damage cells, while radio waves are harmless. Radio carries broadcasts and Wi-Fi, microwaves cook food and relay phone signals, infrared is felt as heat and used in remote controls and thermal cameras, ultraviolet causes tanning and sterilises, X-rays image bones, and gamma rays treat cancer.
Worked example: using c = fλ, a radio station at 100 MHz has wavelength 3 × 10⁸ / 10⁸ = 3 m, whereas green light at 5.5 × 10¹⁴ Hz has wavelength about 550 nm. Wavelengths range from kilometres for long radio waves to less than a trillionth of a metre for gamma rays.
Different waves are produced by different processes, from oscillating circuits to nuclear decay. A misconception is that radio waves and light are different kinds of thing; they are the same phenomenon at different frequencies. Another is that all radiation is dangerous; only the high-frequency end is ionising.
Key ideas
- Radio, microwave, infrared, visible, UV, X-ray, gamma
- All travel at c in vacuum
- Higher frequency means more energy
Quick check
Use cases: where Electromagnetic Spectrum helps
- Homework: review the key idea behind Electromagnetic Spectrum before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Electromagnetic Spectrum without notes.
- Visual learning: play with the interactive lab to see how Electromagnetic Spectrum changes when you adjust its inputs.
- Teaching a friend: explain Electromagnetic Spectrum 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 Spectrum?
Light is one band of electromagnetic waves ordered by frequency.
What will I learn in Electromagnetic Spectrum?
Radio, microwave, infrared, visible, UV, X-ray, gamma. All travel at c in vacuum. Higher frequency means more energy.
Is Electromagnetic Spectrum 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 Spectrum 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 Spectrum?
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.