About

In radio frequency (RF) engineering, acoustics, and optics, the relationship between a wave's frequency and its physical length is governed by the speed of propagation in the medium. Accurate wavelength calculation is critical for designing antennas, where a mismatch of even a few millimeters can drastically increase Standing Wave Ratio (SWR) and reduce transmission efficiency. Similarly, in acoustics, understanding the wavelength of sound in different materials helps in designing effective soundproofing and concert hall architectures.

This tool determines the wavelength (λ) based on the input frequency and the selected propagation medium. Unlike basic calculators that assume a vacuum environment, this utility accounts for the velocity factor of various media, such as coaxial cables (where signals travel slower than light) or water (where sound travels faster than in air).

Formulas

The fundamental relationship between wavelength, frequency, and wave velocity is expressed as:

λ = vf

Where:

λ = Wavelength (m)
v = Phase Velocity in the medium (m/s)
f = Frequency (Hz)

For electromagnetic waves in transmission lines, the velocity is often defined by a Velocity Factor (VF):

v = c × VF

Reference Data

Medium	Type	Propagation Velocity (v)	Velocity Factor (VF)
Vacuum / Free Space	EM Wave	299,792,458 m/s	1.00
Air (Radio)	EM Wave	≈ 299,700,000 m/s	0.9997
Coaxial Cable (Solid PE)	EM Wave	≈ 197,863,000 m/s	0.66
Coaxial Cable (Foam PE)	EM Wave	≈ 239,833,966 m/s	0.80
Optical Fiber (Silica)	Light	≈ 200,000,000 m/s	0.67
Water (20°C)	Sound	1,481 m/s	N/A
Air (20°C)	Sound	343 m/s	N/A
Steel	Sound	5,960 m/s	N/A

Frequently Asked Questions

The frequency of a wave is determined by the source and remains constant. However, the speed at which the wave travels changes depending on the density and electromagnetic properties of the material (permittivity and permeability). Since wavelength is speed divided by frequency, if speed decreases (like light entering glass), the wavelength must shorten.

Velocity Factor (VF) represents the speed of an electrical signal in a cable relative to the speed of light in a vacuum. For example, a standard RG-58 coaxial cable has a VF of roughly 0.66, meaning the signal travels at 66% of the speed of light. Antenna elements made of wire also have a VF slightly less than 1 due to the "end effect".

For electromagnetic waves in a vacuum, no. For sound waves, yes, significantly. The speed of sound in air increases with temperature. This tool uses standard values at 20°C for acoustic mediums.

Yes. Divide the resulting full wavelength by 4. Quarter-wave vertical antennas are common because they are compact and use the ground plane to mirror the other half of the dipole.