Calculate wavelength, frequency or speed of light with EM spectrum region
Wavelength (λ) is the distance between consecutive peaks (or troughs) of a wave. For electromagnetic radiation, the relationship is λ = c / f, where c is the speed of light (≈ 2.998 × 10⁸ m/s in vacuum) and f is the frequency. This means wavelength and frequency are inversely proportional: higher frequency → shorter wavelength. The electromagnetic spectrum spans from gamma rays (wavelengths < 10 pm, frequencies > 30 EHz) through X-rays, UV, visible light (400–700 nm), infrared, microwaves, to radio waves (wavelengths > 1 m, frequencies < 300 MHz). The energy of a photon relates to frequency via E = hf (Planck's equation) where h = 6.626 × 10⁻³⁴ J·s.
Visible light occupies a narrow band: violet (380–450 nm), blue (450–495 nm), green (495–570 nm), yellow (570–590 nm), orange (590–620 nm), red (620–750 nm). This tool calculates wavelength from frequency or vice versa, converts between units (nm, μm, mm, m), and indicates where the result falls in the electromagnetic spectrum — with the corresponding color if in the visible range.
In vacuum, all electromagnetic waves travel at c ≈ 3 × 10⁸ m/s regardless of frequency. In a medium (glass, water, air), the speed is v = c/n where n is the refractive index (glass n ≈ 1.5, water n ≈ 1.33). When light enters a medium, frequency stays constant (it's set by the source) but wavelength changes: λ_medium = λ_vacuum / n. This is why light bends at interfaces (Snell's law) — different wavelengths travel at slightly different speeds, causing dispersion (rainbows, prisms).
The human eye has three types of cone cells peaking at ~420 nm (blue), ~530 nm (green), and ~560 nm (red). Color perception is the brain's interpretation of which cones are stimulated. The visible spectrum is: violet 380–450 nm, blue 450–495 nm, green 495–570 nm, yellow 570–590 nm, orange 590–620 nm, red 620–750 nm. Wavelengths outside this range are invisible: below 380 nm is UV (ultraviolet), above 750 nm is IR (infrared). "White light" is a mixture of all visible wavelengths.
Radio bands are defined by frequency (FM radio: 87.5–108 MHz; 4G LTE: 700 MHz–2.7 GHz; 5G: up to 52.6 GHz) because frequency determines channel spacing, bandwidth, and propagation characteristics. But antenna design uses wavelength: a half-wave dipole antenna is λ/2 long. Lower frequency = longer wavelength = larger antenna but better range through obstacles. Higher frequency = shorter wavelength = smaller antenna but more data capacity (larger bandwidth).
Photon energy E = hf = hc/λ (h = Planck's constant = 6.626 × 10⁻³⁴ J·s). Shorter wavelength = higher frequency = higher energy. UV photons (λ ≈ 300 nm) have enough energy to break chemical bonds — causing sunburn (DNA damage) and photochemistry. X-ray photons (λ ≈ 0.1 nm) can ionize atoms. Infrared photons (λ ≈ 10 μm) are too low energy to ionize — they only cause heating (thermal radiation). This is why UV/X-ray are "ionizing radiation" and radio/IR are "non-ionizing."
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