Question

eli creates longitudinal waves in the spring toy.
select the true statements about longitudinal waves.
a longitudinal wave carries energy.
if a longitudinal waves frequency decreases and its speed stays the same, its wavelength increases.
if a longitudinal waves amplitude increases, the energy carried by the wave decreases.
in a longitudinal wave, the wave and the particles of matter move in parallel directions.

Explanation:

1. All waves, including longitudinal ones, transfer energy through a medium, so the first statement is true.
2. Using the wave equation $v = f\lambda$, if speed $v$ is constant and frequency $f$ decreases, wavelength $\lambda$ must increase to maintain equality, so the second statement is true.
3. Wave energy is proportional to the square of amplitude ($E \propto A^2$), so increasing amplitude increases energy, making the third statement false.
4. By definition, longitudinal waves have particles oscillating parallel to the wave's direction of travel, so the fourth statement is true.

Answer:

A. A longitudinal wave carries energy.
B. If a longitudinal wave's frequency decreases and its speed stays the same, its wavelength increases.
D. In a longitudinal wave, the wave and the particles of matter move in parallel directions.