From kilometre-long radio waves to gamma rays smaller than an atom, the whole electromagnetic spectrum is one continuum travelling at one speed, c. Drag the wavelength slider or hit a preset and watch the band, frequency and photon energy update through c = fλ and E = hc/λ.

The Electromagnetic Spectrum: One Continuum, One Speed

Radio waves and gamma rays are the same phenomenon separated only by scale, and this simulator lets you sweep across the whole range with a single move. Drag the wavelength slider λ from roughly 100 km down to one picometre and watch the band name, frequency, photon energy in eV, and energy in joules update together. The preset buttons jump you straight to familiar landmarks: FM radio, a microwave oven, visible green, X-ray, and gamma. Every point along the scale obeys the same rule, because all electromagnetic waves travel at one fixed speed in a vacuum, c = 2.998 × 108 m/s, no matter their frequency.

That constant speed links wavelength and frequency through c = fλ, so f = c/λ: shorten the wavelength and the frequency climbs. Photon energy follows directly, E = hf = hc/λ, using Planck's constant h = 6.626 × 10-34 J·s. Reading the slider from long to short, the bands run radio, microwave, infrared, visible, ultraviolet, X-ray, gamma, with energy rising the whole way. Visible light occupies only a thin strip near 380 to 700 nm, a sliver of the full range.

The exam trap is brightness. A photon's energy is set by its frequency, not by how intense the source looks; a brighter green lamp emits more photons, each carrying identical energy. Check the numbers with the Photon Energy calculator and the Wave Speed calculator, then explore more with our interactive labs.

Frequently asked questions

What is the electromagnetic spectrum?

It is the full range of electromagnetic waves, ordered by wavelength and frequency: radio, microwave, infrared, visible light, ultraviolet, X-rays and gamma rays. All are the same kind of wave, differing only in wavelength.

Do all electromagnetic waves travel at the same speed?

In a vacuum, yes — every band travels at the speed of light, c = 2.998 x 10^8 m/s, regardless of frequency. Wavelength and frequency are linked by c = f times lambda.

How is a photon's energy related to its wavelength?

By E = hc/lambda, where h is Planck's constant. Shorter wavelengths mean higher frequencies and higher photon energy, so gamma rays carry far more energy per photon than radio waves.

Does a brighter light source give higher-energy photons?

No. Brightness sets the number of photons, not their energy. A brighter source of the same colour emits more photons, each carrying exactly the same energy.

References & formula source

  • Halliday, Resnick & Walker — Fundamentals of Physics, Chapter 33 (Electromagnetic Waves).
  • Young & Freedman — University Physics with Modern Physics, §32.1 (Maxwell's Equations and Electromagnetic Waves; the spectrum).
  • R. Nave — HyperPhysics, Georgia State University, "Electromagnetic Spectrum" section.