chapter 1: waves

Chapter 1: WavesWaves interact and transfer energy in predictable ways

1.1 Waves transfer energy•How forces cause waves•How waves transfer energy•How waves are classified

wavea disturbance that transfers energy from one place to another

waves transfer energy over distance without moving matter the entire distance

Where Do Waves Get Energy?

Vibration-Any movement that follows the same path repeatedly. An object that is vibrating is moving. A force causes the vibration.

An object that is moving has energy.A vibrating object gives off some of its

energy to nearby particles. This movement of energy from a vibrating source outward is a wave.

Waves get their energy from a vibration.

VibrationsExample: The top of a drum vibrates

after it is struck by a drum stick. It moves up and down several times creating sound.

Example: Your ear drum vibrates in response to sound which enables you to hear.

mediumany substance that a wave moves through

ex. water, the ground, a rope, air

Waves Through Matter and SpaceMedium-Matter or substance

through which a wave is transmitted.Water is a medium for ocean waves.Air is a medium for sound waves.All phases of matter solids, fluids,

plasmas, can act as a medium.

mechanical wavesany wave that transfers energy through matter (must have matter to work)

wavelength

transverse wavesthe direction in which the wave travels is perpendicular to the direction of the disturbance

longitudinal wavethe wave travels in the same direction as the disturbance

1.2 Waves have measurable properties•how amplitude, wavelength and frequency are measured•how to find a wave’s speed

Amplitudethe distance between a line through the middle of a wave and a crest or trough.

see p. 17

wavelengththe distance from crest to crestor trough to trough

frequencythe number of wavelengths passing a fixed point in a certain amount of time (usually a second)

Waves / second (hertz)

Wave speedspeed = wavelength x frequencyS = λ ∙ f

5 QQDraw a transverse wave.Label the wavelength.Label the amplitude.Draw a low amplitude transverse wave and a high frequency transverse wave.

Draw a longitudinal wave, label the rarefactions.

Name Amplitude Wavelength Frequency WaveSpeed

1.3 Waves behave in predictable ways•How waves change as they encounter a barrier•What happens when waves enter a new medium•How waves interact with other waves

reflectionthe bouncing back of a wave after it strikes a barrier

refractionthe bending of a wave as it enters a new medium

occurs because waves travel at different speeds in different mediums

diffractionthe spreading out of waves through an opening or around an obstacle

interferencewaves interact with other wavesthey can add energy to, or take energy away from each other

the meeting and combining of waves

Suppose that you create a wave by moving a rope up and down. What will happen if you increase the energy you put into the rope? What will happen if you increase the speed of the motion?amplitude, frequency, wavelength

wavelengthfrequencyamplitudereflectionrefractiondiffractionmediumdisturbanceforcehertzmechanical wavewave

transverse wavelongitudinal waveinterferencecresttroughvibrationconstructive

interferencedestructive

interferencewave speedcompressionrarefactionwaves / second