Reflection and Mirrors - Mission RM3 Detailed Help

Abe, Bev, Cis, Don, Eva and Flo (shown in RED) sit in front of a plane mirror; their image locations are shown (in PINK). Which students can Abe see? List the first letters of each visible student (from Abe's vantage point, and including Abe).

Line of Sight
Line of sight - it is a simple idea, but a very powerful idea once you get a grasp of it. To see anything, you must sight at the thing. To see an image, you must sight at the image. When you sight at the thing - whether the image or some other object - light from the thing travels along a line to your eye. Your eye and the thing you are looking at are two points on the line of sight along which you are looking.

In order for Abe to view an image of himself or others in the mirror, Abe must sight along a line at the image location. And when he does, light from the corresponding object must be able to reflect off the mirror at the location where his line of sight intersects the mirror. But what happens if Abe's line of sight doesn't intersect the mirror when Abe sights at an image? The image of that person cannot be seen. Using the simple line of sight principle discussed in the Know the Law section, you can make very accurate predictions as to who Abe can see.

To be successful on this question, you will need to use a straight-edge placed upon the computer monitor. The edge of a sheet of paper works great. The paper will allow you to see if the lines of sight intersect the mirror. It is important to look at the computer monitor perpendicularly. This is always a good measurement technique - looking at a dial or meter head-on. Looking at the monitor (or a meter or a dial) at another angle can give a faulty measurement. Bend over or tilt your monitor to get an accurate perspective.


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