Hobbies And Interests
Home  >> Science & Nature >> Science

The Physics of How Tri-Fold Mirrors Work

One of the reasons light is so useful is that, although it can do some pretty complicated things, it operates according to fairly straightforward rules. That might be hard to believe when you stand between two mirrors that face each other almost perfectly, and you can see a reflection of yourself going off into infinity, but that̵7;s just a simple rule being applied over and over again with each reflection. Tri-fold mirrors operate by those same simple rules.

  1. The Law of Reflection

    • One of the most straightforward of all the physical rules governing the behavior of light is the law of reflection: ̶0;The angle of incidence equals the angle of reflection.̶1; That is, if you measure the angle between the incoming light beam and a line perpendicular to the plane of the mirror, the reflected beam will be at that same angle, on the other side of the line perpendicular to the mirror. In physics terminology, that perpendicular line is called the ̶0;normal̶1; to the surface.

    Two Hinged Mirrors

    • When two mirrors are hinged so their edges are lined up with each other, the reflection changes as the angle between the mirrors changes. First, imagine the two mirrors are folded flat with their reflective sides facing inside like the covers of a book -- call that zero degrees. Open the mirrors so they̵7;re at right angles to each other -- that̵7;s ninety degrees. Then keep opening the mirrors until they̵7;re both flat, facing you -- that̵7;s one hundred eighty degrees. The number of reflections created by the hinged mirrors is given by the formula: number = (360 / angle) -1.

    Mirrors at One Hundred Twenty Degrees

    • The typical tri-fold mirror has each of the side mirrors at an angle of one hundred twenty degrees with respect to the center mirror. By the formula from the previous section, this means each of the two angled pairs (the left-center and the right-center) produce 360/120 - 1 = 2 reflections. That means that the left mirror will show you one reflection and the center will show you one reflection. The same holds true for the right and center, but it̵7;s the same one reflection in the center, so a trifold mirror will show you three separate images. If you keep your shoulders square to the center mirror and turn your head to the left and right, this allows you to see your profile without having to twist your body around.

    Ninety Degrees

    • If the angle of the side mirrors was set to ninety degrees, then each of the two angled pairs would produce 360/90 -1 = 3 reflections. The three reflections on the left pair are the direct reflection in the left mirror, the direct reflection in the center mirror, and the reflection of the reflections you see right at the junction of the two mirrors. The reflection at the junction, because it̵7;s ̶0;reversed̶1; with each of the two reflections, looks the way that others see you, with your right hand appearing to be on the left side of the reflection facing you. In this configuration there will be five reflections: one direct reflection from each side and one double reflection at each mirror junction.

Science
Science

https://www.htfbw.com © Hobbies And Interests