📡 เครื่องคิดเลขความยาวคลื่นและความถี่

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Every wave obeys the same simple relationship: its speed equals its wavelength times its frequency, so wavelength λ = c / f and frequency f = c / λ. For electromagnetic waves in a vacuum the speed is the speed of light, c = 299,792,458 m/s (about 3 × 10⁸ m/s). Because that product is fixed, wavelength and frequency are inversely related — higher frequency always means shorter wavelength. This calculator converts either way, reports the period (T = 1 / f) and the photon energy, and names the electromagnetic band the result falls in, from radio through microwave, infrared, visible light, ultraviolet, X-ray and gamma ray.

As a worked example, an FM radio station at 100 MHz (10⁸ Hz) has a wavelength of λ = 3 × 10⁸ / 10⁸ = 3 metres — which is why FM antennas are on the order of a metre long. Green light at about 5.5 × 10¹⁴ Hz has a wavelength near 545 nm, squarely in the visible band. The tool also returns each photon’s energy from E = h × f, using Planck’s constant h = 6.62607015 × 10⁻³⁴ J·s, and shows it in both joules and electron-volts.

Higher-frequency light carries more energy per photon, which is why blue and ultraviolet light can drive chemical reactions and damage skin while radio waves cannot. You can also override the wave speed under advanced options to model waves in other media — light in glass, or sound in air — where the propagation speed differs from that of light in a vacuum. These conversions are fundamental to radio and antenna design, optics, spectroscopy and understanding the electromagnetic spectrum.