Which quantity related to energy of a wave measures distance from the rest position to the crest?

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

Answer: (A)

Amplitude is the distance from the rest position to the crest (or trough) of a wave. This height tells how big the wave is, and energy carried by the wave increases with amplitude—specifically, energy grows with the square of the amplitude. The other properties describe how fast the wave moves (velocity), how often it repeats (frequency), and how far apart crests are (wavelength), but they don’t directly measure how much energy the wave carries.