Date post: | 03-Jan-2016 |
Category: |
Documents |
Upload: | jason-andrews |
View: | 217 times |
Download: | 2 times |
Chapter 29Chapter 29
Light WavesLight Waves
1.1. HUYGENS' PRINCIPLEHUYGENS' PRINCIPLE
Every point on a wave front can be regarded as a new source of wavelets, which combine to produce the next wave front, whose points are sources of further wavelets, and so on.
Huygen’s Principle can be used to explain the propagation of wave
fronts involved in reflection, refraction, and diffraction.
.
.
.
.
.
.
.
Consider several points on the wave front
to be sources of secondary wavelets.
.
.
.
.
.
.
.
2.2. DIFFRACTIONDIFFRACTION
The bending of light that passes around an obstacle or through a narrow slit, causing the light to spread and to produce light and dark fringes.
Demo - Laser, diffraction accessories, and Demo - Laser, diffraction accessories, and rainbow disks rainbow disks
If the wavelength of water waves are small
compared to the size of an ocean vessel, the
vessel will cast a “shadow.”
For the same waves a stick will not cast a
“shadow.”
Long wavelengths bend a great deal around small objects.
Because of diffraction AM radio waves travel farther than FM radio waves.
Microscopy diffraction limit -
One cannot see details of objects that are approximately the same size as or smaller than the wavelength of the illuminating light.
3.3. INTERFERENCEINTERFERENCE
SlideSlide - Interference Transparencies - Interference Transparencies
Demo - Finger slit interferenceDemo - Finger slit interference
Demo - Single-color thin film interferenceDemo - Single-color thin film interference
Demo - Optical flats and sodium lampDemo - Optical flats and sodium lamp
Demo - Newton's rings and phase reversalDemo - Newton's rings and phase reversal
Interference Colors by Reflection from Thin Films
Iridescence - the phenomenon of seeing
colors by interference in thin films.
Demo - Soap bubbles and pipeDemo - Soap bubbles and pipe
Demo - Peacock feathersDemo - Peacock feathers
Example - Coated photographic lenses
Interferometers measure small distances.
Thin Film t
Air
Air
Phase Reversal
upon reflection
Path Difference = 2t = n for destructive interference
Thus t = n(/2)
n = 1,2,3,4,…… You see the complement of whichever color is destructively interfered with.
4. POLARIZATION
Video - Polarization DiagramPolarization Diagram Video - Crossed PolaroidsCrossed Polaroids Demo - PolaroidsDemo - Polaroids
Light waves are transverse. This is verified by polarization.
Common sources of light are not polarized. Polaroid Crystals - one axis direction
absorbs, one transmits. Polarized glare occurs on reflection from
nonmetallic surfaces.
COLORS BY TRANSMISSION THROUGH POLARIZING MATERIALS
Video - Crossed Polaroids and Crystal Video - Crossed Polaroids and Crystal Video - Polarizers and StressVideo - Polarizers and Stress Demo - Polaroids and accessoriesDemo - Polaroids and accessories
Three-Dimensional Viewing
Stereoscopic viewersSlideSlide - Stereogram
5. HOLOGRAPHY
Hologram means whole message.
Demo - Reflection hologramDemo - Reflection hologram
Demo - Transmission hologramDemo - Transmission hologram
No lenses are used for imaging in the
creation or the viewing of a hologram.
Object and source both illuminateboth illuminate all of the
photographic plate.
The light used to make the hologram
must be coherent.
A hologram is an interference pattern.
It is best to use coherent light when viewingviewing a
hologram.
A hologram can be divided.
One gets a magnified holographic image by
viewing a hologram with a longer of light
than was used in creating the hologram.
Chapter 29 Review QuestionsChapter 29 Review Questions
AM band radio waves travel farther than FM band radio waves because
(a) AM waves travel faster than FM waves(b) AM wavelengths are shorter than FM
wavelengths(c) AM waves are scattered more than FM
waves(d) AM waves are diffracted more than FM
waves
(d) AM waves are diffracted more than FM waves
If laser light passes by a hair, a pattern of light and dark can be seen on a properly placed screen. What phenomenon (phenomena) is (are) being observed?
(a) diffraction
(b) polarization
(c) chromatic aberration
(d) all of the above
(e) none of the above
(a) diffraction
Polaroid sunglasses worn in a normal viewing position will eliminate polarized
glare.
(a) vertically
(b) horizontally
(c) all
(b) horizontally
Red is bent the most when it travels through a
(a) light pipe (optical fiber)
(b) prism
(c) grating
(c) grating
Two polaroids that have their polarization axes at 45o to each other will still allow light to pass through.
(a) True
(b) False
(a) True
The point where a soap bubble bursts will be black just as it bursts.
(a) True
(b) False
(a) True