31 Mar, 2013
In a cube
PRESENTATION: An optical system is a set of surfaces that separate materials with distinct refractive indexes and that can be: reflective (mirrors) if they reflect most of the light reaching them; or refractive (diopters) if they refract most of the light reaching them. One of the simplest optical systems is a flat mirror that gives a direct virtual image of an object, which is the same size and the same distance in absolute values as the object itself.
- Rearview Mirror Dimming Function, William Layton, Phys. Teach. 49, 578 (2011)
- The mirror box, Gene Thompson and Don Mathieson, Phys. Teach. 39, 508 (2001)
INTRODUCTION: In Physics, Geometrical Optics is based on Snell’s (or Descartes’ according to some sources) phenomenological laws of reflection and refraction. Using these, you only have to do some trigonometry with the light rays to obtain the formulas that correspond to mirrors, diopters, and lenses (or combinations of these), and so obtain the laws that govern the optical instruments we are all familiar with.
OBJECTIVE: To demonstrate that you can see yourself from any direction in a three-cornered mirror.
MATERIALS: Three square mirrors (12x12cm2), glue, or sticky tape.
SETUP: The three, square, 12x12cm2 mirrors are stuck together using the glue or sticky tape in such a way that they are all at right-angles to each other.
EXPLANATION: A mirror is a polished surface that reflects light hitting it according to the laws of reflection. The simplest example is a flat mirror although there are also concave or convex mirrors. In a three-cornered mirror, the rays of light hit the mirrors from any direction and leave in the opposite direction to the one they hit it from. This is due to the angle existing between the mirrors. As a result of this, we can see ourselves in the mirror from any angle at which we can see the mirror itself.
CONCEPTS: Geometrical optics, Snell’s laws, reflection phenomenon.
- WIKIPEDIA 1
- WIKIPEDIA 2
- YOUTUBE 1
- YOUTUBE 2
- WAKE FOREST UNIVERSITY
- UNIVERSITY OF IOWA
- TEXAS UNIVERSITY
- PHYSLET 1
- PHYSLET 2
- R. Serway, Física, Mac Graw Hill, 2010.
- P. Tipler, Física para la Ciencia y la tecnología, Reverté, 2012.
- R. Ehrlich, Turning the World Inside Out and 174 Other Simple Physics Demonstrations, Princeton University Press, 1997.
STUDENTS 2011-2012: José Ramón Vidal, Roberto Vilariño, Ana Vilas
LINK pdf STUDENTS (In Spanish):