Waves

What’s In a Wave? A wave is a disturbance/movement that transfers energy through matter or space.  Waves DO NOT transfer matter, but they DO transfer energy Ex: ‘The Wave’ in a stadium A wave is a disturbance/movement that transfers energy through matter or space.  Waves DO NOT transfer matter, but they DO transfer energy Ex: ‘The Wave’ in a stadium

Waves and Energy A wave will travel as long as it has energy to transfer Ex: pebble in a pond - ripples soon die out A wave will travel as long as it has energy to transfer Ex: pebble in a pond - ripples soon die out

A medium is the matter a wave travels through. solid, liquid or gas Not all waves need a medium - Electromagnetic waves - travel through space Waves that can only travel through matter - MECHANICAL waves Transverse & Longitudinal A medium is the matter a wave travels through. solid, liquid or gas Not all waves need a medium - Electromagnetic waves - travel through space Waves that can only travel through matter - MECHANICAL waves Transverse & Longitudinal

 You can think of a wave as a moving series of high points and low points.  A crest is the high point of the wave.  A trough is the low point.  You can think of a wave as a moving series of high points and low points.  A crest is the high point of the wave.  A trough is the low point.

Amplitude, Frequency and Wavelength

Amplitude  The amplitude is the maximum height the wave rises above the level surface.  The more energy a wave has the greater its amplitude.  The amplitude is the maximum height the wave rises above the level surface.  The more energy a wave has the greater its amplitude.

Frequency  The frequency of a wave is the rate at which every point on the wave moves up and down.  Frequency means “how often”.  Measured in cycles per second, or hertz (Hz)  The frequency of a wave is the rate at which every point on the wave moves up and down.  Frequency means “how often”.  Measured in cycles per second, or hertz (Hz)

Wavelength  Wavelength is the distance from any point on a wave to the same point on the next cycle of the wave.  The distance between one crest and the next crest is a wavelength.  Wavelength is the distance from any point on a wave to the same point on the next cycle of the wave.  The distance between one crest and the next crest is a wavelength.

Wavelength

Period The time required for one cycle of a wave. A complete motion that returns to its starting point. Measured in units of time (seconds, minutes, hours) The time required for one cycle of a wave. A complete motion that returns to its starting point. Measured in units of time (seconds, minutes, hours)

The speed of waves The speed of a water wave is how fast the wave spreads, NOT how fast the water surface moves up and down or how fast the dropped ball moves in the water. How do we measure the wave speed?

Speed v = f frequency (cycles/sec) wavelength (m) speed (m/sec)

Mechanical Waves TR ansverse: Matter in the medium moves back and forth at right angles to the direction the wave is moving  ex: Ocean Waves TR ansverse: Matter in the medium moves back and forth at right angles to the direction the wave is moving  ex: Ocean Waves

Mechanical Waves Longitudinal: Matter in the medium moves back and forth in the same direction the wave is moving  ex: Earthquake waves Also known as Compressional Waves Longitudinal: Matter in the medium moves back and forth in the same direction the wave is moving  ex: Earthquake waves Also known as Compressional Waves

Transverse Wave

Transverse and Longitudinal Waves A transverse wave has its oscillations perpendicular to the direction the wave moves. A longitudinal wave has oscillations in the same direction as the wave moves. A transverse wave has its oscillations perpendicular to the direction the wave moves. A longitudinal wave has oscillations in the same direction as the wave moves.

Transverse waves The oscillations of a transverse wave are not in the direction the wave moves.

Longitudinal waves The oscillations of a longitudinal wave are in the same direction that the wave moves.

Four wave interactions When a wave encounters a surface, four interactions can occur: reflection, refraction, diffraction, or absorption. When a wave encounters a surface, four interactions can occur: reflection, refraction, diffraction, or absorption.

Wave animations  mos/waves/wavemotion.html mos/waves/wavemotion.html  mos/waves/wavemotion.html mos/waves/wavemotion.html