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