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'A' Level Medical Option Questions - The Ear

Q6. The diagram shows a vertical section through a human ear.

(a) Name and state the functions of the parts labelled A, B and C in the diagram.

A: ear drum or tympanic membrane

This transfers the vibration of sound waves into mechanical oscillations

B: ossicles

These are a system of levers to multiply the force

OR system of levers to link outer and inner ear

C: cochlea

This converts the pressure wave in the fluid into an electrical signal

(6 marks)

(b) An ear has a threshold of hearing at a particular frequency at an intensity level of 42 dB. Calculate the intensity of sound incident on the ear.

I0 = 1.0 × 10–12 W m–2

intensity level = 10 log10(I/Io)

42 = 10 x log10 (I/(1.0 x 10-12))

I = 104.2 x 1.0 x 10-12

I = 1.6 x 10-8 W m–2

(2 marks)

(Total 8 marks)