Properties of Waves Chapter 11: Section 3

Learning Targets Explain how energy is transferred through a wave Give examples of mechanical and non-mechanical waves Describe the different types of waves

Introduction So why does this happen? When a pebble is dropped into water, small waves travel away from the area where the pebble was dropped If you examined the motion of a leaf floating near this disturbance, you would see that the leaf moves around but always returns its original position So why does this happen?

Wave Motion Ripple waves in a pond start with a disturbance at some point causing water on the surface to move These waves travel outward in a circular pattern away from the original disturbance

Note that the medium does not actually travel with the waves In this example, the water in the pond is the medium through which the wave travels Air can also act as an effective medium Note that the medium does not actually travel with the waves After the wave has passed, the medium returns to its original position

Mechanical Waves Most waves require a medium in which to travel These types of waves are known as mechanical waves Electromagnetic waves, such as visible light, radio waves, microwaves, and X rays, do not require a medium and can travel through a vacuum

Wave Types A wave that consists of a single traveling pulse is called a pulse wave If you continue to generate pulses at one end of a rope a periodic wave forms.

Transverse Waves A wave in which the particles of the medium move perpendicularly to the wave motion, is called a transverse wave Example: Slinky, “the wave”, water waves

Longitudinal Waves When particles of the medium vibrate parallel to the direction of wave motion, the wave is called a longitudinal wave Example: Compressed and stretched regions that travel along a spring Sound waves are an example of a longitudinal wave

Waves Transfer Energy Waves transfer energy by the vibration of matter rather than the motion of matter As the waves spread out, particles in the medium transfer their vibrations from one particle to the next Thus waves transfer energy from one place to another while the medium remains in essentially the same place

Waves are often able to transport energy efficiently The rate of energy transfer depends on the amplitude at which the particles of the medium are vibrating. The greater the amplitude, the more energy a wave carries