Op Art

In preparation for the Op Art panel please read over the following links about Op Art and  two of the most influential artists in the movement  and answer the following questions:

NOTE:My advice is to type your answers in a google doc and then copy and paste the answers in the comments section below this post.

What is Op Art?
When did the movement take place?
Who was Victor Vasarely (when did he live, where was he from, what media did he use, what type of shapes did he use,was his work primarily color or black and  white)?
Who was Bridget Riley(when did she live, where was she from, what media did she use, what type of shapes did he use,was his work primarily color or black and white)??
How are thier works similar? how do they differ?
What is your personal opinion of Op Art?
Add a link to your favorite example of Op art.

Definitions about the Op Art Movement:

http://en.wikipedia.org/wiki/Op_art
http://www.moma.org/collection/theme.php?theme_id=10139
http://arthistory.about.com/cs/arthistory10one/a/op_art.htm

Here is a very interesting site based on Op Art and how artists are using it in music, style, and other areas:
http://www.op-art.co.uk/

Info about Victor Vasarely and his art:
http://www.guggenheim.org/new-york/collections/collection-online/show-full/bio/?artist_name=Victor%20Vasarely&page=1&f=Name&cr=1
http://www.guggenheim.org/new-york/about/guggenheim-images/show-list/artist/v/?search=Victor%20Vasarely

Info about Bridget Riley and her art:
http://www.moma.org/collection/artist.php?artist_id=4929
http://www.webexhibits.org/colorart/riley.html
http://nadav.harel.org.il/Bridget_Riley/