6 The Eye and Ear

The Human Ear

One of the jobs of the human ear is to detect sounds (it also tells you which way up you are). The ear has a number of features that make it especially good at detecting longitudinal sound waves.
The outer ear, or pinna is the bit that sticks out at the sides of your head. This part of the ear collects the sound waves and directs them into the ear canal. At this stage the sound is just a series of vibrations in the air.

The ear drum then starts to vibrate - causing three small ear bones to vibrate in turn.

The sound wave then passes through another membrane to the cochlea which turns the sound vibrations into electrical signals ... these travel along nerves to the brain.

 after Pople and Williams: Science to GCSE

Now answer these questions ...

  1. What is the job of the pinna ?
  2. Where would you find a pinna ?
  3. Where do the sound waves go next ?
  4. What is inside the ear canal ?
  5. What is at the end of the ear canal ?
  6. What do the sound waves normally cause the ear-drum to do ?
  7. What is on the other side of the ear-drum ?
  8. How many ear bones are there ?
  9. What structure do the ear bones connect to ?
  10. What does the cochlea do ?

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The Human Eye

The job of the human eye is to collect light waves and turn them into nerve signals that can be understood by the brain. The first job of the eye, though, is to focus the light into the right place.

The transverse light waves are refracted first by the cornea.
The light waves then travel through a transparent liquid until they meet the lens. The shape of the lens can be changed by a ring of muscles that surround it. The lens then finely focusses the light waves.

The focussed light travels through a transparent jelly until they meet the light-sensitive retina. The cells of the retina change the light waves into electrical signals. These pass along the optic nerve to the brain.

Because the retina is so sensitive ... the amount of light entering the eye through the pupil is controlled by the iris. On really sunny days (remember them?) the iris causes the pupil to get smaller - letting less light in.

 after Pople and Williams: Science to GCSE

Now answer these questions

  1. What sort of waves does the eye detect ?
  2. What sort of wave is light ?
  3. What does the cornea do ?
  4. What is another name for bending light ?
  5. What sort of substance does the light travel through next ?
  6. What does the fine focussing of the light ?
  7. Can the lens change shape ?
  8. What sort of substance does the light travel through next ?
  9. What is the light-sensitive part of the eye called ?
  10. What does the retina do ?

You scored out of 10 on that test