Home : Waves : Eye & 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.
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
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.