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Translations, Rotations, and Reflections

Move figures on the coordinate plane using patterns.

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Practice Translations, Rotations, and Reflections
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Mirror, Mirror

Credit: Frank Kovalchek
Source: http://www.flickr.com/photos/72213316@N00/6168294960/
License: CC BY-NC 3.0

When was the last time you looked at your reflection? This morning, before you left the house? Maybe between classes, when you ducked into the bathroom to fix your hair? Nowadays, most people take mirrors for granted, but for thousands of years, only the very wealthy ever had a chance to see them.

From Rocks to Factories

According to archaeologists, people first made mirrors about 10,000 years ago. The ancient residents of Turkey polished obsidian to make mirrors. Obsidian is a black volcanic rock that is categorized as a volcanic glass. Later, people made mirrors out of polished metals such as copper, silver, and gold. However, these metals were very expensive, and only wealthy people could afford them. Mirrors were rare and expensive until 1835, when a German inventor discovered a way to attach a thin sheet of precious metal to the back of a piece of glass. Soon, factories mass-produced mirrors, and rich and poor alike could afford to have several mirrors in their homes.

Credit: Jose and Roxanne
Source: http://www.flickr.com/photos/53196116@N00/3447534527
License: CC BY-NC 3.0

Mirrors aren't just good for checking your appearance. They revolutionized the design of microscopes and telescopes (pictured above are six mirror segments of the James Webb Space Telescope). Your dentist uses a mirror to see behind your teeth and to check for cavities. Cars use mirrors to make headlights seem brighter. Mirrors can be used to reflect and direct the sunlight. One remote Scandinavian village is using mirrors to light up the town square in the wintertime.

See for yourself: http://www.rawstory.com/rs/2013/10/27/giant-mirrors-bring-winter-sun-to-norwegian-village-for-the-first-time-in-its-history/

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Watch the following videos to learn more about the application of mirrors in telescopes, periscopes, and even a solar-powered "death ray" supposedly invented by Archimedes.




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Image Attributions

  1. [1]^ Credit: Frank Kovalchek; Source: http://www.flickr.com/photos/72213316@N00/6168294960/; License: CC BY-NC 3.0
  2. [2]^ Credit: Jose and Roxanne; Source: http://www.flickr.com/photos/53196116@N00/3447534527; License: CC BY-NC 3.0

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