Question

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

Explanation:

• A medium is the matter through which a wave travels. So, the statement "The matter that a longitudinal wave travels through is called the medium" is correct.
• The formula for wave speed is \(v = f\lambda\) (where \(v\) is speed, \(f\) is frequency, and \(\lambda\) is wavelength). If \(v\) is constant (\(v = f_1\lambda_1=f_2\lambda_2\)), when \(f\) decreases (\(f_2 \lambda_1\)). So, the statement "If a longitudinal wave's frequency decreases and its speed stays the same, its wavelength decreases" is incorrect.
• In a longitudinal wave, the particles of the medium move parallel to the direction of wave propagation. So, the statement "In a longitudinal wave, the wave and the particles of matter move in parallel directions" is correct.
• The energy of a wave is related to its frequency (\(E = hf\), where \(h\) is Planck's constant). As frequency \(f\) increases, energy \(E\) increases. So, the statement "If a longitudinal wave's frequency increases, the energy carried by the wave increases" is correct.

Answer:

• The matter that a longitudinal wave travels through is called the medium.
• In a longitudinal wave, the wave and the particles of matter move in parallel directions.
• If a longitudinal wave's frequency increases, the energy carried by the wave increases.