In a sine wave, the frequency describes cycles per second.

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

Answer: (B)

Frequency is the rate at which a sine wave repeats over time, i.e., how many cycles occur each second. This is exactly what “cycles per second” describes, and it’s measured in hertz (Hz). Wavelength is about the spatial length of one cycle along the medium, not how often it repeats. Phase is about where in the cycle you start or the relative shift between waves. Amplitude is how far the wave displacement reaches from rest, relating to height or loudness, but not how often it repeats. If you know the wave speed, you can relate frequency and wavelength with the equation v = fλ, but the phrase “cycles per second” directly identifies frequency.