Relative Wavelength:
The relative wavelength of a radio wave is the ratio of its wavelength to the wavelength of a standard reference wave. This reference wave is usually taken to be the wavelength of light in a vacuum, denoted by the symbol "λ0." The relative wavelength is expressed as a multiple of λ0 and is denoted by the symbol "λr."
For example, if a radio wave has a wavelength of 10 meters and the wavelength of light in a vacuum is 0.0000005 meters, then the relative wavelength of the radio wave is:
λr = λ / λ0 = 10 meters / 0.0000005 meters ≈ 20,000,000
This means that the wavelength of the radio wave is 20,000,000 times longer than the wavelength of light in a vacuum.
Frequency:
Frequency, denoted by the symbol "f," is a measure of how often a radio wave repeats itself over time. It is expressed in units of Hertz (Hz), which represent the number of cycles per second.
The frequency of a radio wave is inversely proportional to its wavelength, meaning that as the frequency increases, the wavelength decreases. This relationship can be expressed mathematically as:
f = c / λ
where:
- f is the frequency in Hertz (Hz)
- c is the speed of light in a vacuum (approximately 299,792,458 meters per second)
- λ is the wavelength in meters
For example, if a radio wave has a frequency of 10 MHz (10 million cycles per second) and the speed of light is 299,792,458 meters per second, then the wavelength of the radio wave is:
λ = c / f = 299,792,458 meters per second / 10,000,000 cycles per second ≈ 30 meters
In summary, the relative wavelength and frequency of a radio wave provide information about its position in the electromagnetic spectrum and its physical properties. The relative wavelength compares its wavelength to a reference standard, while the frequency measures how often the wave repeats itself over time.