Download III. Wave Properties of Light

Chs. 17 & 18 - Waves
III. Wave Behaviors
 Reflection
 Refraction
 Diffraction
 Interference
A. Reflection
Normal
Reflection
when a wave
strikes an object
and bounces off
incident beam
reflected beam
A. Reflection
Inversion
A 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 mirror
A type of transverse wave
A. Reflection
Ultrasonic waves
Ultrasound Medical Imaging
SONAR
“Sound Navigation Ranging”
A. Reflection
RADAR
Radio detection and ranging
A. Reflection
Reverberation
echo effect produced
by the reflection of
sound
Anechoic chamber designed to eliminate
reverberation.
B. Refraction
Refraction
bending of waves when passing
from one medium to another
caused by a change in speed
• slower (more dense)  light
bends toward the normal
• faster (less dense)  light
bends away from the normal
SLOWER
FASTER
B. Refraction
Surface waves (ocean waves)
Do not travel throughout the entire medium
Refracted as the water depth changes
Bends 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
overlap
constructive 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 Optics
Total 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!
Rainbows
refraction-reflection-refraction
E. Cool Applications!
Diffraction Gratings
glass or plastic made up
of many tiny parallel slits
may also be reflective
spectroscopes, reflective
rainbow stickers, CD
surfaces
E. Cool Applications!
Thin Films - Bubbles & Oil Slicks
interference results from double reflection
E. Cool Applications!
Blue Sky & Red Sunsets
• Molecules in atmosphere
scatter light rays.
• Shorter wavelengths (blue, violet)
are scattered more easily.
SUNSET
• more atmosphere
• more scattering
• orange-red sky & sun
NOON
• less atmosphere
• less scattering
• blue sky, yellow sun
E. Cool Applications!
Resonance
special case of forced
vibration
object is induced to
vibrate at its natural
frequency