11 Does a wave travel on forever? Energy may spread out as a wave travels What happens to a wave?Does a wave travel on forever?NOEnergy may spread out as a wave travels
12 Waves are related to vibrations Waves are caused by vibrating objects. Waves and vibrationsWaves are related to vibrationsWaves are caused by vibrating objects.
13 Particles in a medium can either vibrate Transverse andLongitudinal WavesParticles in a medium can either vibrateperpendicularlyparallelto the direction of wave motion
14 EXAMPLES: Stadium wave, light wave Transverse andLongitudinal WavesTransverse WavesThe particles of the medium vibrate perpendicularly to the direction the wave travels.EXAMPLES: Stadium wave, light wave
15 Transverse andLongitudinal WavesLongitudinal WavesThe particles of the medium vibrate parallel to the direction the wave travels.EXAMPLES: Sound Waves
16 Transverse andLongitudinal WavesIn a surface wave, particles move in a circle. (perpendicularly and parallelSurface waves occur at the boundary of two mediums
18 Wave Properties For a sine or transverse wave: Crests – high points Troughs – low pointsAmplitude – distance from the midpoint to the crest (or from the midpoint to the trough)Wavelength – distance between 2 consecutive pts. of a wave (nm)Frequency - how often a vibration occurs (Hz)
19 Frequency determines the pitch of the sound Wave PropertiesFrequency determines the pitch of the soundAmplitude determines how loud or soft a sound seems to be.
20 Wave PropertiesFrequency – The number of wavelengths that pass a fixed point each second.Measured in Hertz (Hz)For example:20 vibrations/second is the same as 20 Hz.150 Hz is the same as 150 vibrations/second.
21 Wave PropertiesThe wave period is the amount of time it takes for a wavelength to pass a point.As the frequency of a wave increases, the wave period decreases.Periods are measured in units of seconds.
22 Wave PropertiesThe speed of a wave depends on the medium it is traveling through.It can be calculated using the following equation:Speed (in m/s) = frequency (in Hz) x wavelength (in m)ORv = f x λ
23 Wave Interactions Waves can experience four types of interactions 1) Reflection2) DiffractionRefractionInterference
24 Wave Interactions Reflection The bouncing back of a wave as it meets a boundary. Waves reflect at a free boundary When a wave hits a fixed boundary, it is reflected and turned upside down to travel back in the opposite direction
25 Wave InteractionsDiffraction - Bending of a wave as it passes an edge or an opening.**Stays in the same medium
26 Wave InteractionsRefraction The bending of waves as they pass from one medium to another.**Change mediums.Example, fish underwater, or looking at fish in an aquarium.
27 Wave InteractionsINTERFERENCE This occurs when several waves are in the same location and combine to produce a single, new wave that is different from the original wave.Interference of Sound waves creates beats in the music
28 InterferenceWave Interference – When 2 or more waves interact, it results in interference.Interference can be:ConstructiveDestructive
29 InterferenceConstructive Interference When the crest of one wave overlaps the crest of another wave, they reinforce each other, and create a wave with an added amplitude.Amplitudes are added.
30 Interference Destructive Interference When the crest of one wave meets the trough of another wave; they detract from each other, and create a wave with decreased amplitude.Amplitudes are subtracted.
31 Interference Standing Waves Wave form that appears to not move along the mediumCreates regions of no vibration (nodes) (Complete destructive interference)Creates regions of maximum vibration (antinodes) (Complete constructive interference)