12.1 THE NATURE OF THE WAVES

Waves transfer energy without transferring matter . We also use waves to transfer information. Examples include a phone and a radio.

There are many different types of waves. These include :

sound waves, waves, waves on springs and ropes, and sesimc waves produced by earthquakes. All these waves are examples of mechanical waves. Mechanical waves are vibrations which travel through a medium which is a substance.

Light waves, radiowaves and microwaves are all examples of Electromagnetic waves.

When the waves travel through a substance, the substance itself doesn't travel. You can prove this by observing the waves on a rope. You should see :

When a small object is dropped in the , the waves spread out on . The waves travel through the surface but the does not travel away from the object.
When a tuning vibrates so sound waves travel through the air away from the tuning . The air itself doesn't travel away from the vibrating object. If it did, a vaccum would be created.

TRANVERSE WAVES

The waves on a rope and the ripples on the surface of are called transverse waves becaue the vibrations ( also called oscillations) move up and down or from side to side. All electromagnetic waves are tranverse waves.

The oscillations of a tranverse waves are perpenducalar to the direction in which the waves transfer energy

LONGITUDINAL WAVES

We can use a splinky spring to demonstrate to how sound waves travel. When one end of splinky is pushed in and out repeatedly, vibrations travel through the spring. The oscillations are parallel to the direction in which the waves transfer energy. These waves are called longitudinal waves.

Sound waves that travel through the air are longitudinal waves. When an object vibrates in air, it makes the air around it vibrate as it pushes and pulls on air. The oscillations (compressions and rarefractions) that travel through the air are sound waves. The oscillations are in the direction in which the wave travels.

The oscillations of a longitudinal wave are parallel to the direction in which the waves transfer energy.

Mechanical waves can be tranverse or longitudinal.

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