What are Waves? Building Science Champions

In thought On a separate sheet of paper, write a paragraph about how surfers are able to use waves for their sport.

Objectives Define waves and identify what causes them Identify and compare the three main types of waves.

Key Terms Wave Mechanical waves Medium Vibration Transverse wave Wavelength Crest Trough Longitudinal wave Compression Rarefaction Surface wave

What are Waves? Wave – is a disturbance that transfers energy from one place to another without transferring matter. All waves spread out and transfer energy from the source of the energy What is the energy source of these waves? Raindrops In which direction is the light transferred from the candle? In all directions

Mechanical Waves A mechanical wave can only travel through matter Mechanical waves can travel through a solid, liquid or gas Mechanical waves cannot travel through a vacuum Medium – a material which a wave can travel through Two types of mechanical waves – transverse and longitudinal Vibration – is a repeated back-and-forth or up-and- down motion

Transverse Wave Transverse wave – is a wave in which the disturbance is perpendicular to the direction the wave travels Draw the picture and label the parts of the transverse wave with the words from the next slide

Parts of a Transverse Wave (LIGHT) Crest – highest points on a transverse wave Trough – the lowest point on a transverse wave Rest position – when no disturbance or vibration is present Direction of disturbance can be up-and-down or side-to-side Direction of travel is the direction the wave travels from the energy source Wavelength – from crest to crest or trough to trough

Transverse Wave

Longitudinal Wave(sound) Longitudinal wave – makes the particles in a medium move parallel to the direction that the wave travels Draw the picture of the longitudinal wave and label the wave with the words from the next slide

Parts of a Longitudinal Wave Compressions – the regions of a longitudinal wave where the particles in the medium are closest together Rarefactions – the regions of a longitudinal wave where the particles in the medium are the farthest apart Wavelength – from compression to compression

Longitudinal Wave

Surface Waves Surface waves – combinations of transverse and longitudinal waves Surface waves occur at the surface between 2 mediums, such as water and air When waves pass through water, water moves up and down, like transverse waves on a rope. The water moves back and forth in the direction the wave is traveling, like the coils on a spring. Unlike a spring water does not compress.

Vibrations and Mechanical Waves Vibrating objects, such as beating a drum or strumming a guitar, are the sources of energy that produce a mechanical wave Each vibration makes a wave After an object stops vibrating, waves continue to move Water waves are a combination of transverse and longitudinal waves

Seismic Waves Seismic waves are produced when parts of Earth’s upper layers move along a fault

Electromagnetic Waves Electromagnetic wave – is a wave that can travel through empty space (vacuum) and through matter The type of electromagnetic waves given off by an object depends mainly on the temperature of the object Infrared and visible light carry the sun’s radiant energy Draw the electromagnetic spectrum

Review There are three types of waves Waves are created by energy

References Anderson, M. et all (2012) Physical Science. McGraw-Hill: Columbus Frank, D.V et al (2001). Physical Science. Prentice Hall: New Jersey