Which quantity is measured in hertz?

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

Answer: (A)

Hertz measures how often something repeats in one second. That makes it a unit for frequency—the number of cycles or oscillations per second. For waves, frequency is how many wave crests pass a point each second, so a higher pitch sound has a higher frequency and is described in hertz. For example, a tuning fork vibrating at 440 Hz repeats 440 times each second. Wavelength, on the other hand, is the distance between successive crests and is measured in meters. Amplitude is how far the wave moves from rest, measured in displacement or pressure units, not in hertz. Energy is the capacity to do work and is measured in joules.