Waves A wave can be described as a disturbance that transfers energy Some waves require a medium A medium is a substance or material that carries the wave.

Medium the medium is composed of parts that are capable of interacting with each other. The interactions of one particle of the medium with the next adjacent particle allow the disturbance to travel through the medium. In the case of a sound wave in air, the particles or interacting parts of the medium are the individual molecules of air. in the case of a stadium wave the medium are the fans

A Wave Transports Energy and Not Matter When there is a disturbance moving through a medium, the individual particles of the medium are only temporarily displaced from their rest position.

The particles of matter in the medium return to their fixed position. Waves are seen to move through an ocean or lake; yet the water always returns to its rest position. Energy is transported through the medium, yet the water molecules are not transported.

A wave transports its energy without transporting matter.

Types of waves A transverse wave is a wave in which particles of the medium move in a direction perpendicular to the direction that the wave moves A longitudinal wave is a wave in which particles of the medium move in a direction parallel to the direction that the wave moves.

Electromagnetic versus Mechanical Waves An electromagnetic wave is a wave that is capable of transmitting its energy through a vacuum (i.e., empty space). Example: light, x rays

Mechanical waves Mechanical waves require a medium in order to transport their energy from one location to another. Ex: sound, ocean waves, earthquakes

Parts of a transverse wave

amplitude of a wave refers to the maximum amount of displacement of a particle on the medium from its rest position.

Parts of a longitudinal wave

In the case of a wave, the speed is the distance traveled by a given point on the wave (such as a crest) in a given interval of time. In equation form,

If the crest of an ocean wave moves a distance of 20 meters in 10 seconds, then the speed of the ocean wave is 2.0 m/s. On the other hand, if the crest of an ocean wave moves a distance of 25 meters in 10 seconds (the same amount of time), then the speed of this ocean wave is 2.5 m/s. The faster wave travels a greater distance in the same amount of time.

Frequency vs. Period Frequency refers to how often something happens. Frequency is a rate quantity Frequency is the cycles/second Frequency is measured in Hertz

Period refers to the time it takes something to happen. Period is a time quantity. Period is the seconds/cycle. Period is measured in time