Explain how the human ear detects sound waves and converts them into signals that are sent to the brain.

WJEC A-Level Physics (Wales) — 5.3 Electric and magnetic fields (A-Level only) · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

The outer ear (pinna) collects sound waves and directs them into the ear canal.
The waves reach the eardrum, a thin membrane, and cause it to vibrate.
The vibrations are transmitted to the three ossicles (malleus, incus, stapes) which amplify and oscillate.
The stapes pushes on the oval window of the cochlea, a fluid‑filled organ; the resulting fluid waves stimulate hair cells.
The hair cells convert the mechanical vibrations into electrical impulses that travel along the auditory nerve to the brain.

Examiner tips

  • Use the exact sequence of structures: pinna → eardrum → ossicles → cochlea → auditory nerve.
  • Show the conversion from mechanical to electrical signals in the cochlea.
  • Mention the role of the ossicles as amplifiers.
  • Use UK spelling (e.g., ‘cerebellum’ if needed).

Common mistakes

  • Confusing the role of the eardrum with the cochlea; the eardrum only vibrates, not convert signals.
  • Omitting the ossicles or describing them incorrectly.
  • Using vague terms like ‘sound travels’ instead of ‘vibrations are transmitted’.

Mark scheme (5 marks)

  1. The outer ear (pinna) collects / gathers the sound waves
  2. Sound waves cause the ear drum (thin membrane) to vibrate
  3. Vibrations of the ear drum cause the ear bones to oscillate
  4. The oscillations travel through the fluid-filled cochlea, where cells convert the vibrations into electrical signals
  5. The electrical signals are transferred to the brain via the auditory nerve

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