What is the distance, measured in the direction of propagation of a wave, between two successive points in the wave?

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

Answer: (B)

Wavelength is the spatial distance between two identical points of a wave that are in the same phase, measured along the direction the wave travels. In a traveling wave, that means the distance from one crest to the next crest (or from one trough to the next trough) or any equivalent pair of identical points in the wave cycle. It represents the length of one complete wave cycle in space. The wave’s speed is the product of its frequency and its wavelength, so knowing one helps determine the others (speed = frequency × wavelength). Amplitude is how high the wave displacement is (its height), period is the time for one complete cycle at a fixed point, and frequency is how many cycles pass a point per second. For example, if a wave moves at 340 m/s with a frequency of 20 Hz, its wavelength is 340 / 20 = 17 meters.