Frequency ____ affect propagation speed.

Frequency ____ affect propagation speed.

• A. Always affects
• B. Sometimes affects
• C. Does not affect
• D. Only at high frequency

Answer: (C)

Propagation speed in a non-dispersive medium is independent of frequency. The speed is set by the medium’s electromagnetic properties, so in air or vacuum it stays essentially the same for all frequencies used in typical communications. What changes with frequency is the wavelength, since λ = v / f. For example, if the speed is about 3×10^8 m/s, doubling the frequency halves the wavelength, but the travel speed remains the same. Only in dispersive media, where the medium’s refractive index varies with frequency, would speed depend on frequency. In the common context of free-space or non-dispersive propagation, the correct statement is that frequency does not affect propagation speed.

Propagation speed in a non-dispersive medium is independent of frequency. The speed is set by the medium’s electromagnetic properties, so in air or vacuum it stays essentially the same for all frequencies used in typical communications. What changes with frequency is the wavelength, since λ = v / f. For example, if the speed is about 3×10^8 m/s, doubling the frequency halves the wavelength, but the travel speed remains the same. Only in dispersive media, where the medium’s refractive index varies with frequency, would speed depend on frequency. In the common context of free-space or non-dispersive propagation, the correct statement is that frequency does not affect propagation speed.