# If radio waves are invisible to the human eye, how can one measure wavelength?

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If radio waves are invisible to the human eye, how can one measure wavelength?

In: Physics Radio waves move the speed of light, and their wavelength is the inverse of their frequency. So you can measure the frequency and use the simple relationship (speed of light) = wavelength x frquency.

In practice, an easy way to learn the wavelength or frequency of a radio wave is to use an antenna (which is why radios have them). The radio waves push the electrons in the antenna back and forth as they hit it. So you can hook that antenna up to an amplifying circuit and look at the electronic wave instead of the radio wave itself. This is easily done with an oscilloscope. You can build electronic detectors that can detect a peak and then count the time it takes for another peak. Since the speed at which the wave moved is known you can calculate wavelength. All radiation (visible light included) are measured indirectly with equip that turns the energy into electric signals. And all radio signals have a direct relationship between their frequency and wavelength. So if you know the frequency then you can calculate the wavelength. Then once you know the wavelength you can build an antenna to specifically receive that frequency/wavelength. The length of a radio antenna (think car) is specifically designed to receive a narrow range of frequencies/wavelengths.