Images by Reflection

[Fu-Kwun Hwang]

We can understand a mirror image using a ray diagram.

The image in the following simulation shows several light rays,
1, that originated by diffuse reflection at the person's nose. They bounce off the mirror, producing new rays,
2. To anyone whose eye is in the right position to get one of these rays, they appear to have come from a behind the mirror,
3, where they would have originated from a single point. This point is where the tip of the image-person's nose appears to be.
A similar analysis applies to every other point on the person's face, so it looks as though there was an entire face behind the mirror. The customary way of describing the situation
requires some explanation:

* Customary description in physics: There is an image of the face behind the mirror.
* Translation: The pattern of rays coming from the mirror is exactly the same as it would be if there was a face behind the mirror. Nothing is really behind the mirror.

This is referred to as a virtual image, because the rays do not actually cross at the point behind the mirror. They only appear to have originated there.

Embed a running copy of this simulation
<applet code='users.ntnu.fkh.optics_flatmirror_pkg.optics_flatmirrorApplet.class' archive='http://www.phy.ntnu.edu.tw/ntnujava/ejsuser/2/ejs_optics_flatmirror.jar' name='optics_flatmirror7919' id='optics_flatmirror7919' width='496' height='400' mayscript=true><param name='draggable' value='true'></applet>
Embed a running copy link(show simulation in a popuped window)
<a href='http://www.phy.ntnu.edu.tw/ntnujava/msg.php?smfejs=7919' target='smfejs'>Run simulation</a>

Full 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

• Please feel free to post your ideas about how to use the simulation for better teaching and learning.
• Post questions to be asked to help students to think, to explore.
• Upload worksheets as attached files to share with more users.

Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!

You can click the mouse in the right side of the mirror, and the simulation will draw 3 traces to find the image (follow the trace of mouse when you drag it).

The following is a flash movie (show you how to play with it). Enjoy it!


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