Waves n Bellringer: What is A wave? (define, use Ch.22 in your book to help you) n What is an example of a wave?

General definitions of vibrations and waves n Vibration: in a general sense, anything that switches back and forth, to and fro, side to side, in and out, off and on, loud and soft, or up and down is vibrating. A vibration is a wiggle in time. n Wave: a vibration in both space and time is a wave. A wave extends from one place to another. n Vibrations and waves: the source of all waves is something that is vibrating. Waves are the result of vibrations throughout space.

-Waves can be classified by WHAT they move through or by HOW energy moves through them. - There are two classifications for waves based on what they move through: n Mechanical Waves n Electromagnetic Waves

-Mechanical waves are waves that can ONLY move through a medium (through matter). -Mechanical waves require the particles of the medium to vibrate in order for energy to be transferred. n water waves n earthquake/seismic waves n sound waves n waves that travel down a rope or spring -All of these examples CANNOT move through empty space.

-Electromagnetic waves are waves that can travel through matter or empty space where matter is not present. -Empty space is space in which NO MATTER is present. Another name for this is a vacuum. n radio waves n microwaves n infrared waves n visible light n ultraviolet rays n X-rays

There are two classifications for waves based on how energy moves through them: Longitudinal Waves Transverse Waves

-Mechanical waves in which the particles of matter in the medium vibrate by pushing together and moving apart parallel to the direction in which the wave travels are called longitudinal waves. n sound waves n some waves in a spring n some seismic waves n some Electromagnetic waves

n n Rarefactions- particles in a longitudinal wave are spread apart n n Compressions- particles in a longitudinal wave are compressed (pushed) together

Sound Waves Molecules in the air vibrate creating the compressions and rarefactions.

Mechanical waves in which the particles of matter in the medium vibrate by moving back and forth and perpendicular (at right angles) to the direction the wave travels are called transverse waves. n strings on a musical instrument n waves on a rope n some waves in a spring n some seismic waves

n Crest- highest point of the wave n Trough- Lowest point of the wave

Parts of a wave n Wavelength is the distance from any point on a wave to the same point on the next cycle of the wave. n The distance between one crest and the next crest is a wavelength. (crest to crest, trough to trough, rarefaction to rarefaction, compression to compression)

Parts of a wave n The frequency of a wave is the rate at which every point on the wave moves up and down. n Frequency means “how often”.

Parts of a wave n The amplitude of a wave is the maximum height the wave rises above the level surface.

Constructive interference Reinforcement when the crest of one wave overlaps the crest of another Their individual effects adds together, resulting in a wave increased in amplitude

Destructive Interference Cancellation when crest of one wave overlaps trough of another reducing their individual effects

Exit Assignment n On your notebook paper draw a longitudinal wave. Label- rarefaction, compression, amplitude, and wavelength. Give two examples of longitudinal waves. n Draw a transverse wave. Label- crest, trough, amplitude, and wavelength. Give two examples of transverse waves. n Turn your paper in.