Light Polarization
Feb 22, 2016
Light Polarization
These three are the same…
• Light *pure energy
• Electromagnetic Waves*energy-carrying waves emitted
by vibrating electrons• Photons
*particles of light
Polarization Light:
Waves in only one direction
Not polarized light:
waves in random scatter
Blue sky has some glare or polarization
How do we make Polarized Light?
Light Polarization
Parallel, crossed, 45 degrees(100%, 0%, 70%)
Each Polaroid pick only 1 direction of light
What is crossed?
• Two polaroid filters at 90 degrees to another• No light gets through• First vertical filter blocks horizontally polarized light• Second horizontal filter blocks remaining vertical light
How do we make Polarized Light?I. Polarizers- Polarizers are made of long
chained molecules which absorblight with electric fields perpendicular to the axis.
How do we make Polarized Light?II. Reflections off non-metals
How do we make Polarized Light?III. Refraction-
-light bending
-some calcite minerals
How do we make Polarized Light?II. Reflections off non-metals
What happened to that blue sky?
Less and less b lue
No blue left if look long ways across sky like at sunrise and sunset
Space=dark=no air to scatter light
Polarized sunglasses
Most road glare is horizontally polarized
Polarized 3-d glasses
(weaker effect if use different colors/prisms)
Check your understanding
• Suppose that light passes through two Polaroid filters whose polarization axes are parallel to each other. How does the final light compare to the original?A. 100% of original
• B. ½ light• C. ¼ light
D. no light
Check your understanding
• Light becomes partially polarized as it reflects off nonmetallic surfaces such as glass, water, or a road surface. The polarized light consists of waves vibrating in a plane that is ____________ (parallel, perpendicular) to the reflecting surface.
A. Parallel b. perpendicular
Check your understanding
• Which sunglasses work best for glare
• A. both vertically polarizedb. both horizontally polarized
• C. one side of each• D. dark shades unpolarized
Demos:
projector lightcorn syrup
plastic rulerscotch tape
polaroid filmscell phone display
glare on windows/clockcomputer screen