In a longitudinal wave, the wavelength is determined by specific characteristics of the wave:
1. Height of the amplitude: This option is incorrect because amplitude refers to the maximum displacement of points on a wave, which conveys the energy of the wave, not its wavelength.
2. Total length of the wave: This option is also incorrect. The total length might encompass several wavelengths, but it does not define what a single wavelength is.
3. Distance between compressions: This option is correct. In longitudinal waves, such as sound waves, compressions are regions where the particles are closest together. The distance between two successive compressions (or two successive rarefactions) is defined as the wavelength.
4. Distance between crests and troughs: This option is incorrect because crests and troughs are features of transverse waves, not longitudinal waves.
Therefore, the correct method to find the wavelength of a longitudinal wave is by measuring the distance between compressions. Thus, the correct answer is the third option:
Distance between compressions.
