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