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| • 1 − Acoustic waves or sound waves in air •
Here are audio waves transmitted through air. For "radio waves and light waves" − scroll down ↓ Conversion: frequency f to wavelength λ and wavelength to frequency c is the speed of sound waves (*or* can be the speed of light and radio waves) |
| If instead of the speed of light, the speed of sound in air c = 343 m/s at 20°C is used, the following conversions apply. |
| Fill out the gray box above and click on the calculation button of the respective column. The proposed speed of sound c = 343 m/s or 1125.33 ft/s can be changed here. The currently accepted value is c = 331.29 meters per second at 0 degrees Celsius; established in 1986. |
| Sometimes when you switch from m to cm to ft and inch the answer is wrong the first time. Toggle between the changed values. Do a reset and try again. |
Formulas and Equations: c = λ × f λ = c / f = c × T f = c / λ
| Physical value | symbol | unit | formula |
| frequency | f = 1/T | Hz = 1/s | f = c / λ |
| wavelength | λ | m | λ = c / f |
| time period or cycle duration |
T = 1/f | s | T = λ / c |
| wave speed | c | m/s | c = λ × f |
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Conversion of period to frequency and back
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The top open range of the frequency spectrum for sound waves
| • 2 − Radio waves and light waves in a vacuum •
Conversion: frequency f to wavelength λ and wavelength to frequency c is the speed of light waves and the speed of radio waves in a vacuum |
| If instead of the speed of sound in air, the speed of light c = 299 792 458 m/s is used, the following conversions apply. |
Fill out the gray box above and click on the calculation button of the respective column.
The proposed speed of light c = 299 792 458 m/s or 983 571 056 ft/s can be changed here.
Formulas and Equations: c = λ × f λ = c / f = c × T f = c / λ
Wave frequency in Hz = 1/s and wavelength in nm = 10−9 m
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| Radio wave frequency and microwave radiation are both forms of energy called electromagnetic radiation. Sunshine contains three other forms of electromagnetic radiation: ultraviolet rays, infrared (heat) waves, and visible light waves. These electromagnetic waves spread in a vacuum at the speed of light ≈ 300 000 km/s as electromagnetic radiation. The velocity of propagation of electric signals via optical fibres is nearly 2/3 of the speed of light, which means ≈ 200 000 km/s. In theory electrical signals move at the speed of light. Cables only slow them down. The velocity propagation factor: VOP = 1 ⁄ √ε, Epsilon is the dielectric constant, which is for polyethylene dielectrics (PVC) nearly 1.4. Sound is also shown at the spectrum chart, but it is no electromagnetic radiation. Sound pressure is the deviation from the local ambient pressure caused by a sound wave - mainly in air. The speed of sound is 343 m/s at 20°C in air. |
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Spectrum of Electromagnetic Radiation
| Region | Wavelength Angstroms |
Wavelength centimeters |
Frequency Hz |
Energy eV |
| Radio | > 109 | > 10 | < 3×109 | < 10−5 |
| Microwave | 109 − 106 | 10 − 0.01 | 3×109 − 3×1012 | 10−5 − 0.01 |
| Infrared | 106 − 7000 | 0.01 − 7×10−5 | 3×1012 − 4.3×1014 | 0.01 − 2 |
| Visible | 7000 − 4000 | 7×10−5 − 4×10−5 | 4.3×1014 − 7.5×1014 | 2 − 3 |
| Ultraviolet | 4000 − 10 | 4×10−5 − 10−7 | 7.5×1014 − 3×1017 | 3 − 103 |
| X-Rays | 10 − 0.1 | 10−7 − 10−9 | 3×1017 − 3×1019 | 103 − 105 |
| Gamma Rays | < 0.1 | < 10−9 | > 3×1019 | > 105 |
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The notation "eV" stands for electron-volts, a common unit of energy measure in atomic physics. A graphical representation of the electromagnetic spectrum is shown in the figure below. |
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| Electromagnetic spectrum |
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Thus we see that visible light and gamma rays and microwaves are really the same things. They are all electromagnetic radiation; they just differ in their wavelengths. Sometimes the unit Ångström (angstrom) = 10−10 m = 0.1 nm is used for wavelength. |
Approximate wavelength and frequency ranges of the colors
| Color |
Wavelength nm |
Frequency THz |
| red | 780 - 622 | 384 - 482 |
| orange | 622 - 597 | 482 - 503 |
| yellow | 597 - 577 | 503 - 520 |
| green | 577 - 492 | 520 - 610 |
| blue | 492 - 455 | 610 - 659 |
| violet | 455 - 390 | 659 - 769 |
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1 terahertz (THz) = 103 GHz = 106 MHz = 1012 Hz, 1 nm = 10-3 μm = 10-6 mm = 10-9 m. White light is a mixture of the colors of the visible spectra. |
| Sound waves and electromagnetic waves are different. Sound waves need a medium to travel through, while the electromagnetic waves do not. The properties of a sound wave depend on the properties of the medium it travels through. |
| Approximate speed of sound in common materials |
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| Medium | Speed of sound m/s ft/s |
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| Air, dry at 20 °C | 343 | 1 125 | |
| Hydrogen at 0 °C | 1 280 | 4 200 | |
| Water at 15 °C | 1 500 | 4 920 | |
| Lead | 2 160 | 7 090 | |
| Concrete | 3 100 | 10 200 | |
| Wood (soft - along the fibre) | 3 800 | 12 500 | |
| Glass | 5 500 | 18 500 | |
| Steel | 5 800 | 19 000 | |
| Ohm's law as acoustic equivalent for plane progressive waves Conversion of sound units (levels) |
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