Explain how the human ear works.
Different sounds produced in our surroundings are collected by pinna. The collected sound passes through the auditory canal. At the end of the auditory canal, there is a thin membrane called the eardrum or tympanic membrane. When compression the medium reaches the eardrum the pressure on the outside of the membrane increases and force the eardrum inward. Similarly, the eardrum moves outward when the rarefaction reaches it. The eardrum starts vibrating back and forth rapidly when the sound waves fall on it. The vibrating eardrum sets the small bone hammer into vibration. The vibrations are passed from the hammer to the second bone anvil, and finally to the third bone stirrup. The vibrating stirrup strikes on the membrane of the oval window and passes its vibration to the liquid in the cochlea. This produces electrical impulses in nerve cells. The auditory nerve carries these electrical impulses to the brain. These electrical impulses are interpreted by the brain as sound and we get a sensation of hearing.
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Fig. 8.11
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The speed-time graph for a car is shown is Fig. 8.12.
Fig. 8.12
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