Chapter 11Chapter 11

Section 3Section 3

IntroductionIntroductionWhat happens to a ball when it hits the What happens to a ball when it hits the

wall?wall?How do you think a ball might travel How do you think a ball might travel

differently in water?differently in water?Today you will learn how a wave behaves Today you will learn how a wave behaves

when it hits something or travels through when it hits something or travels through different media!different media!

Behavior of WavesBehavior of WavesReflectionReflection::

Occurs when a wave strikes an object and Occurs when a wave strikes an object and bounces off of itbounces off of it

All waves-All waves---including sound, water, light --including sound, water, light waves waves can be reflectedcan be reflected

Ex: Seeing your self in a mirror, hearing Ex: Seeing your self in a mirror, hearing echoing down an empty hallway etcechoing down an empty hallway etc

What are some other ways you think waves What are some other ways you think waves are reflected?are reflected?

Behavior of WavesBehavior of WavesLaw of ReflectionLaw of Reflection

According the law of reflection the angle According the law of reflection the angle of incidence is equal to the angle of of incidence is equal to the angle of reflectionreflection

For example: when you throw a bounce For example: when you throw a bounce pass in basketball, the angle between the pass in basketball, the angle between the ball’s direction and the normal to the floor ball’s direction and the normal to the floor is the same before and after it bouncesis the same before and after it bounces

Incidence Beam

Reflection Beam

Behavior of WavesBehavior of WavesRefractionRefraction

Is the bending of a wave caused by a Is the bending of a wave caused by a change in its speed as it moves from on change in its speed as it moves from on medium to anothermedium to another. . The greater the The greater the speed change, the more the wave speed change, the more the wave bendsbends

Ex: Pencil in water cup, swimmingEx: Pencil in water cup, swimming

Behavior of WavesBehavior of Waves

DiffractionDiffractionOccurs when an object Occurs when an object

causes a wave to change causes a wave to change direction and bend around itdirection and bend around it

Ex: waves hitting an islandEx: waves hitting an island

InterferenceInterference

DefinitionDefinitionWhen two or more waves overlap When two or more waves overlap

and combine to form a new wave.and combine to form a new wave.Two types:Two types:

Constructive interferenceConstructive interferenceDestructive interferenceDestructive interference

Constructive InterferenceConstructive Interference Happens when the crests of two or more Happens when the crests of two or more

transverse waves arrive at the same place transverse waves arrive at the same place and time and over lap (they add together)and time and over lap (they add together)The amplitude of the new wave is equal to The amplitude of the new wave is equal to

the sum of the amplitudes of the original the sum of the amplitudes of the original waveswaves

Also occurs when the compressions of Also occurs when the compressions of different compressional waves overlapdifferent compressional waves overlapProduces a louder soundProduces a louder sound

Destructive interferenceDestructive interference When the crests of one transverse wave When the crests of one transverse wave

meet the troughs of another transverse meet the troughs of another transverse wave (they subtract from each other)wave (they subtract from each other)

Compressional waves D.I. occurs when Compressional waves D.I. occurs when the compressionthe compression (more dense) (more dense) of one of one wave overlaps with rarefractionwave overlaps with rarefraction (less (less dense) of another wave dense) of another wave producing a producing a reduced amplitudereduced amplitudeDecrease in loudnessDecrease in loudness

Ear protectors accomplish thisEar protectors accomplish this

ResonanceResonanceThe ability of an object to vibrate by The ability of an object to vibrate by

absorbing energy at its natural frequencyabsorbing energy at its natural frequency

Size and shape of an object can change Size and shape of an object can change its resonanceits resonance

PolarizationPolarization—CANT BE FOUND IN —CANT BE FOUND IN BOOK!!BOOK!!

Process of aligning the direction of a Process of aligning the direction of a transverse wave’s vibrationstransverse wave’s vibrations

Ex. Polarized sunglasses commonly used Ex. Polarized sunglasses commonly used for fishingfor fishing