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1. Loud but clear

Animation of wave on rope
Picture 1. Colin can make a wave travel down the rope.
Sound waves
What is a wave?
You can make a simple wave on a piece of rope or elastic. Imagine the rope stretched between two people – Colin and Joanne. If Colin shakes the end of the rope, then the shake travels down the rope. If he does three shakes, then all three of them travel along the rope. So he can send a message or energy to Joanne by shaking the rope. He did this using a wave (picture 1).
Colin sent the message without leaving any permanent effect on the rope. The rope is the same before and after the message. A wave carries energy from one place to another without leaving any permanent change on the substance that carried it.
Types of wave
Interactive graphic of transverse wave
Picture 2. A transverse wave on a rope.

The wave on the rope is an example of a transverse wave. In a transverse wave the medium (in this case, the rope) moves at a right angle to the direction of the wave. That is, as the wave moves from left to right, the rope moves up and down. Other examples of transverse waves are waves on the sea and light waves, which are carried by changing electric and magnetic fields.
Video clip of slinky
Picture 3. A longitudinal wave on a slinky.
Sound is different from these waves. It is a longitudinal wave. When it travels through the air, the particles move backwards and forwards rather than side to side. They move along the same direction as the wave. If the wave is moving from left to right, then the particles vibrate back and forth from left to right. Even so, they are not permanently displaced once the wave has passed by.

Another example of a longitudinal wave is a wave on a slinky.

Interactive graphic cut away of the ear
Picture 4. The outer ear collects the sound, which is amplified in the middle ear and turned to electrical signals in the inner ear.
How do we hear?
When a sound wave reaches Joanne's ear, the moving air particles make her ear drum vibrate. These vibrations are amplified about twenty times by the bones in the middle ear, which act as levers. Finally, the vibrations reach the inner ear where they are turned into electrical signals by the cochlea.

Question 1-1.

Fill in the gaps in the paragraph below. Choose the best answer in each case.

Sound is an example of a wave. It is carried by moving the direction of the wave. It is similar to a wave on .
Summary                   Close
  • Sound is a wave
  • It needs a medium to travel (it won't get through a vacuum)
  • Sound is a longitudinal wave
  • Waves on the sea and on ropes are examples of transverse waves