Ch 10 Section 3

Behavior of Waves

Reflection   When a wave strikes an object and bounces back.

  Reflection in a mirror: Light hits your face and bounces off to a mirror which bounces off and is directed towards your eye.

Echo   A reflection of sound waves

  Bats and dolphins use echo-location to navigate through their environment.

Law of Reflection   Incident beam- light hitting

mirror

  Reflected beam- light bouncing off of mirror

  Angel of incidence is equal to the angle of reflection.

Refraction   Bending of a wave caused by the change in its

speed.   Light moving through a gas to a solid can cause

refraction

Refraction of light in water   Light travels at different speeds in water and air.

This causes refraction of the light.

  Objects appear in different places then they actually are when this occurs

Diffraction   When an object causes a wave to change direction

and bend around it.

  When waves pass around an object

Diffraction   When a wave passes through a narrow opening and

spreads out afterwards.

Diffraction and wavelength   If the object is smaller than the wavelength the

wave diffracts around it.

  If the object is larger than the wavelength the wave does not diffract around it very much

Hearing around corners   You can hear sounds around a corner due to the

diffraction that takes place with the sound waves.   Sound waves are about 1 to 2 feet across; a door is

about 3 feet.   This allows some of the sound waves to diffract

through a doorway.

  Light will not diffract around a corner due to the short wavelength of light.   Light has a λ of 300 to 900nm; this means light

does not diffract around corners of a hallway.

Diffraction of radio waves   AM radio waves have shorter wavelengths than FM

radio waves; this means they can diffract around buildings, hills and other objects.   This gives AM stations better reception.

Interference   When two or more waves overlap to form a new

wave.

Constructive interference   Waves add together

  When the crests of two waves meet

Destructive interference   Waves subtract from one another

  When the crest of one wave meets the trough of another

Standing waves   A wave pattern that

forms when waves of equal wavelength and amplitude travel in opposite directions and interfere with each other.

Standing waves in music   Vibrations of a bow string and a violin create

standing waves from the vibrations.

  Flute creates a standing wave in a column of air.

Resonance   Process by which an object vibrates by absorbing

energy at its natural frequencies.

  If enough energy is absorbed the object can vibrate and break apart.