Unit to measure frequency of a wave, cycles per second.

• A. Wavelength
• B. Hertz
• C. Amplitude
• D. Frequency

Answer: (B)

Measuring how often a wave repeats each second is frequency, the rate at which cycles occur. The standard unit for this rate is the hertz, written Hz. One hertz equals one cycle per second, so if a wave completes 30 cycles in one second, its frequency is 30 Hz. Wavelength describes the distance between adjacent crests (measured in meters) and tells you about the wave's length, not how often it repeats. Amplitude is the height of the wave, related to its energy or loudness, but not its repetition rate. The frequency and wavelength are related through the wave’s speed with the equation v = f λ, but for the unit itself, Hz is the correct choice.