A periscope is an instrument for observation from a concealed position. In its simplest form, it is a tube in each end of which are mirrors set parallel to each other at 45 degree angle.
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1348.0;attach=1557;image[/img]
The size of the image is the same as the object.

[size=16pt]The questions is: What will happen if the object is moving up?
a. The image will move up, too!
b. The image will stay at the same height.
c. The image will move down.[/size]
Make a guess before you play with it and find out the answer by yourself.

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[b]The following is a simulation for periscope[/b] (with two flat mirrors).
Click [b]trace[/b] checkbox to view the trace of light path (which form the image)
You can drag the object at the top right position with your mouse and watch how the light paths changed.

/htdocs/ntnujava/ejsuser/2/users/ntnu/fkh/mirrortwo_pkg/mirrortwo.propertiesFull screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop. This work is licensed under a Creative Commons Attribution 2.5 Taiwan License
Download EJS jar file(1333.2kB):double click downloaded file to run it. (44 times by 26 users) , Download EJS source (9 times by 8 users) View EJS source


For the following case: the same question again
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1348.0;attach=1559;image[/img]
What will happen if the object is moving up?
a. The image will move up, too!
b. The image will stay at the same height.
c. The image will move down.

More information about periscope can be found at http://en.wikipedia.org/wiki/Periscope
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