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Chs. 17 & 18 - Waves
III. Wave BehaviorsReflectionRefractionDiffraction Interference
A. Reflection
Reflectionwhen a wave
strikes an object and bounces off
incident beam reflected beam
Normal
A. Reflection
InversionA transverse wave
traveling to a fixed end or colliding with a denser medium will flip on its way back
A. Reflection
Reflecting light in a mirrorA type of transverse wave
A. Reflection
Ultrasonic waves
Ultrasound Medical Imaging SONAR“Sound Navigation Ranging”
A. Reflection
RADARRadio detection and ranging
A. Reflection
Reverberation echo effect produced
by the reflection of sound
Anechoic chamber - designed to eliminate
reverberation.
B. Refraction
Refractionbending of waves when passing
from one medium to anothercaused by a change in speed
• slower (more dense) light bends toward the normal
SLOWER
FASTER
• faster (less dense) light bends away from the normal
B. Refraction
Surface waves (ocean waves)Do not travel throughout the entire mediumRefracted as the water depth changesBends toward the shore
B. Refraction
Refraction of light depends on…
speed of light in the medium
wavelength of the light - shorter wavelengths (blue)bend more
B. Refraction
Example:
View explanation.
B. Refraction
Example:The “broken” pencil
C. Diffraction
Diffraction
bending of waves around a barrier
Smaller opening = more diffraction
C. Diffraction
longer wavelengths (red, for light) bend more, especially when the opening is small - opposite of refraction
D. Interference
Interference – occurs when 2 or more waves overlapconstructive interference 2 or more waves combine
to produce a wave with larger displacement
Constructive - louder
D. Interference
destructive interference 2 or more waves combine to produce a wave with smaller displacement
Destructive - softer
D. Interference
For light – brighter portions show constructive interference, darker show destructive interference
E. Cool Applications!
Fiber OpticsTotal Internal Reflection
• when all light is reflected back into the denser medium
E. Cool Applications!
The “Broken Pencil”refraction
View animation and explanation of the “Broken Pencil.”
E. Cool Applications!
Rainbowsrefraction-reflection-refraction
E. Cool Applications!
Diffraction Gratingsglass or plastic made up
of many tiny parallel slitsmay also be reflectivespectroscopes, reflective
rainbow stickers, CD surfaces
E. Cool Applications!
Thin Films - Bubbles & Oil Slicksinterference results from double reflection
E. Cool Applications!
Blue Sky & Red Sunsets
NOON• less atmosphere• less scattering• blue sky, yellow sun
SUNSET• more atmosphere• more scattering• orange-red sky & sun
• Molecules in atmosphere scatter light rays.
• Shorter wavelengths (blue, violet) are scattered more easily.
E. Cool Applications!
Resonancespecial case of forced
vibrationobject is induced to
vibrate at its natural frequency
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