# Diffraction Gratings

## Diffraction gratings also generate interference patterns that indicate the wavelength of light passing through.

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3-D photographs

### 3-D Photographs

Credit: Dominic Alves
Source: http://www.flickr.com/photos/64097751@N00/5480234275/

By using principals of interference and diffraction, images that appear three-dimensional to the human eye can be created.

#### Amazing But True

Credit: Shankar S.
Source: http://www.flickr.com/photos/77742560@N06/7448726104

A hologram projected into water [Figure2]

• Holograms, also known as lensless photography, are products of interference and diffraction.
• Holograms are created by taking an incident laser beam and splitting it into two separate beams. While one of the beams is directed at the recording medium, the other beam is directed towards the object. The beam that is directed towards the object is oriented in such a fashion that the scattered light hits the recording medium. When the two beams of light hit the recording medium, an interference pattern is created. The resulting image allows the viewer to see a true 3-D image that will change in appearance when viewed from different angles.
• One amazing fact about holograms is that every single piece of a hologram contains the whole image. This means that even if you cut off a small corner of the hologram, you would still be able to see the entire hologram through the smaller piece!

#### Show What You Know

1. What are the possible results for the amplitude of a resultant wave when two separate waves superimpose?
2. If you wanted to combine two waves in such a way that the resultant wave is zero, what relationship would you have to ensure exists between the two waves?
3. Define classical wave diffraction.

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Color Highlighted Text Notes

1. [1]^ Credit: Dominic Alves; Source: http://www.flickr.com/photos/64097751@N00/5480234275/; License: CC BY-NC 3.0
2. [2]^ Credit: Shankar S.; Source: http://www.flickr.com/photos/77742560@N06/7448726104; License: CC BY-NC 3.0

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