Chs. 17

1
Chs. 17 18 - Waves

• III. Wave Behaviors
• Reflection
• Refraction
• Diffraction
• Interference

2
A. Reflection

• Reflection
• when a wave strikes an object and bounces off

3
A. Reflection

• Inversion
• A transverse wave traveling to a fixed end or
  colliding with a denser medium will flip on its
  way back

4
A. Reflection

• Reflecting light in a mirror
• A type of transverse wave

5
A. Reflection

• Ultrasonic waves

6
A. Reflection

• RADAR
• Radio detection and ranging

7
A. Reflection

• Reverberation
• echo effect produced by the reflection of sound

8
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

9
B. Refraction

• Surface waves (ocean waves)
• Do not travel throughout the entire medium
• Refracted as the water depth changes
• Bends toward the shore

10
B. Refraction

• Refraction of light depends on
• speed of light in the medium
• wavelength of the light - shorter wavelengths
  (blue)bend more

11
B. Refraction

• Example

View explanation.
12
B. Refraction

• Example
• The broken pencil

13
C. Diffraction

• Diffraction
• bending of waves around a barrier
• Smaller opening more diffraction

14
C. Diffraction

• longer wavelengths (red, for light) bend more,
  especially when the opening is small - opposite
  of refraction

15
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
16
D. Interference

• destructive interference ? 2 or more waves
  combine to produce a wave with smaller
  displacement

Destructive - softer
17
D. Interference

• For light brighter portions show constructive
  interference, darker show destructive interference

18
E. Cool Applications!

• Fiber Optics
• Total Internal Reflection
• when all light is reflected back into the denser
  medium

19
E. Cool Applications!

• The Broken Pencil
• refraction

View animation and explanation of the Broken
Pencil.
20
E. Cool Applications!

• Rainbows
• refraction-reflection-refraction

21
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

22
E. Cool Applications!

• Thin Films - Bubbles Oil Slicks
• interference results from double reflection

23
E. Cool Applications!

• Blue Sky Red Sunsets

• Molecules in atmosphere scatter light rays.

• NOON
• less atmosphere
• less scattering
• blue sky, yellow sun

• Shorter wavelengths (blue, violet) are scattered
  more easily.

• SUNSET
• more atmosphere
• more scattering
• orange-red sky sun

24
E. Cool Applications!

• Resonance
• special case of forced vibration
• object is induced to vibrate at its natural
  frequency