Introduction to Mirrors

We have finally finished our exhaustive look into lenses, and started on mirrors. Yesterday, to introduce the topic, we discussed the mirrors kids have at home. When talking about the morning trip to spruce up in front of the bathroom mirror I asked,

“Can you see all of yourself in the bathroom mirror?”

Everyone said they could not. When I inquired as to why, most kids said that there is not enough room to back up to adequately see yourself. So we set off to figure out A) how far back you would have to stand or B) how much of th emir or is required to see all of yourself. In the end we really focused on the latter.

So we measured the distance we stood from the mirror, and the amount of mirror we needed to see all of ourselves.

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Oe student stands away form the mirror and indicates to the student when a dry erase marker lines up with the top of their head, and with the bottom of their feet. Once they gathered 10 points it was time to graph and whiteboard.

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As you can see for the graphs, the slope is nearly zero, meaning that distance does not matter when it comes to seeing all of yourself. Also from the results, you can see the end of our discussion. Before I even brought it up, one group figured out how many inches their y-intercepts came out to, and quickly realized that this was about half of the students height.

After talking about it as a group, students measured their heights, divided by 2, and compared them to their y-intercepts. All were nearly equal!

So we can conclude then that as long as the mirror is half of your height tall, and the top of the mirror is slightly higher or in line with the top of your head, you can stand anywhere and see all of yourself.

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