Wave speed calculator

In one period T = 1/f the wave advances by one wavelength λ. So v = λ/T, and after you substitute T = 1/f you get v = λ·f. That is the same relation as λ = v/f: you only change which quantity is unknown. Here you know the crest spacing and how often crests pass, and you want how fast the medium carries the wave.

Measure λ with microphones at a 440 Hz fork and you get about 0.78 m. The product 0.78 × 440 = 343.2 m/s, about 343 m/s on the page. You have hit sound in air at 20 °C. The pair 0.34 m and 1000 Hz gives 340 m/s, the same order. A 6.86 m bass at 50 Hz returns to 343 m/s again: the same room, a different note.

For radio and light the numbers jump by orders of magnitude. A 3 m dipole and 100 MHz give v = 3e8 m/s. Wi-Fi at 12.5 cm (0.125 m) and 2.4 GHz gives the same c. Type 600 nm light as 6e-7 m; at f = 5e14 Hz the product is 3e8 m/s. If v comes out clearly different from c, the wave is not in vacuum or you typed nanometers as meters.

λ and f have to be positive. The chart of v versus f at fixed λ is a straight line: higher f, larger v, because more cycles per second fit in the same crest spacing. T = 1/f sits beside it, because v = λ/T is the same thought. At 440 Hz, T ≈ 0.00227 s and 0.78 / 0.00227 ≈ 343 m/s.

λ follows the header in m or ft. f stays in hertz. The v result shows m/s and, in US mode, ft/s. On the form, type λ in meters: 600 nm is 6e-7, not 600. The calculator example 0.78 and 440 gives air. 1.48 m and 1000 Hz give 1480 m/s, sound in water.

When you know v and f and want λ (antenna, speaker, color), go back to λ = v/f. A photon from that f is E = h·f. Loudness does not change v: a shout and a whisper travel at the same speed in air.