Wavelength and frequency calculator
Wave speed is wavelength times frequency. For light in vacuum that speed is exactly 299 792 458 m/s by definition.
MHz
m/s
Wavelength
2.997 924 58m
- Half wavelength
- 1.498 962 3
- Quarter wavelength
- 0.749 481 15
- Period
- 1e-8 s
- Photon energy
- 6.6260702e-26
- Photon energy
- 0.000 000 413 566 77 eV
Show the working
- Frequency = 100
- Wave speed = 299 792 000
- f_hz = 100 * 1e6 = 100 000 000
- Wavelength = 299 792 000 / 100 000 000 = 2.997 92
- Quarter wavelength = 2.997 92 / 4 = 0.749 481
- Half wavelength = 2.997 92 / 2 = 1.498 96
- Photon energy = h * 100 000 000 = 6.62607e-26
- Photon energy = 6.62607e-26 / qe = 0.000 000 413 567
- Period = 1 / 100 000 000 = 1e-8
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- v = f lambda
- E = h f, with h exact at 6.626 070 15 x 10^-34 J s
Both c and h are exact by definition under the 2019 SI, so a wavelength from a frequency in vacuum is an exact rational number.
Quarter and half wavelengths matter for antennas: a quarter-wave whip for 100 MHz is 749.5 mm.