Sound Waves
4 marks · NormalA drum is struck once to produce a sound in air. The drum's skin vibrates rapidly after being hit.
State whether the sound wave produced by the drum is longitudinal or transverse.
Explain how the sound travels from the drum to a listener's ear.
Describe what would happen to the sound if the drum was played inside a vacuum.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Longitudinal
(b) Vibrations from the drum make air molecules vibrate; these vibrations pass from molecule to molecule as a longitudinal wave to reach the ear.
(c) No sound would be heard; sound needs particles to travel through, and a vacuum has none.
Common mistakes: Describing sound wave as transverse; Saying sound travels without vibrating air
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies sound wave as longitudinal.
B1 (b) · 1 mark · States vibrations travel through air/particles.
B1 (b) · 1 mark · Indicates vibration is passed from molecule to molecule to the ear as a wave.
B1 (c) · 1 mark · States there is no sound in vacuum or must have particles.
Worked solution
a) The sound wave produced is longitudinal.
b) The vibrating drum skin causes air molecules nearby to vibrate. These vibrations are passed from molecule to molecule, carrying energy through the air as a longitudinal wave to the listener's ear, where the eardrum vibrates.
c) In a vacuum, there are no air molecules for the vibrations to pass through, so the sound would not travel and nothing would be heard.