Question

select the true statements about sound waves. choose 2 answers: a different sound waves can have different amplitudes and frequencies. b sound waves can travel through matter or through vacuum. c human ears cannot hear all sound waves directly. d sound waves travel at the same speed in all mediums.

Explanation:

• For option A: Sound waves are characterized by amplitude (related to loudness) and frequency (related to pitch), and different sound waves can indeed have different amplitudes and frequencies. This is a fundamental property of sound waves.
• For option B: Sound waves are mechanical waves and require a medium (matter) to travel. They cannot travel through a vacuum (which has no matter), so this statement is false.
• For option C: Human ears can only hear sound waves within a certain frequency range (typically 20 Hz - 20,000 Hz). Sound waves with frequencies outside this range (like ultrasonic or infrasonic waves) cannot be heard directly by human ears, so this statement is true.
• For option D: The speed of sound waves depends on the medium (e.g., it's faster in solids than in gases). So sound waves do not travel at the same speed in all mediums, making this statement false.

Answer:

A. Different sound waves can have different amplitudes and frequencies.
C. Human ears cannot hear all sound waves directly.