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# Light

## Light is a small range of the electromagnetic spectrum that we perceive with our eyes.

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Polarizing Light

### Polarizing Light

Credit: Laura Guerin
Source: CK-12 Foundation
License: CC BY-NC 3.0

A polarizer allows only the components that are parallel to the grating to be transmitted through while light that is perpendicular to the polarizer is reflected or absorbed.

#### News You Can Use

Credit: Robert S. Donovon
Source: http://www.flickr.com/photos/booleansplit/2912734656/
License: CC BY-NC 3.0

Photographers use polarizers to darken skies, manage reflections and control light that comes into the camera's lens [Figure2]

• Polarizers are optical filters that only light of a specific orientation can be transmitted while all other orientations are either absorbed or reflected. Normal ordinary light that is given off by the sun or that given off by light bulbs is unpolarized. This means that there is no specific orientation of the light waves. When unpolarized light passes through an optical filter (of any linear orientation), the intensity of the transmitted light is reduced by 12\begin{align*}\frac{1}{2}\end{align*}.  Suppose a second polarizer is placed in line with the light that is transmitted through the first polarizer. The intensity of the light transmitted through the second polarizer, and any subsequent polarizer, is given by

I=I1cos2(θ)\begin{align*}I = I_1 \cos ^2(\theta)\end{align*}

• While most people don’t realize it polarizers can be seen in almost every aspect of your life. Some common examples are:
• sun glasses
• car windshield
• computer screen filters
• glare protectors
• Learn more about the relationship between optical filters and unpolarized light:

#### Show What You Know

1. If light that is polarized along the horizontal axis is incident upon a polarizer that is oriented parallel to the light, what is the percent of intensity that is transmitted?
2. If unpolarized light that initially passed through a polarizer, passes through a 2nd polarizer that is rotated 30° with respect to the first polarizer, derive an expression for the intensity that is transmitted through the 2nd polarizer.
3. Is light a transverse or longitudinal wave?

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