30 Jun, 2013
In a mirror
PRESENTATION: Geometrical optics centres on the study of the propagation of light in different media. Trigonometry is used as a mathematical tool and Fermat’s Principle is the basic physical law that says that a light ray takes the route between two points that requires the least time.
- Creating and Analyzing a Mirage, Lauren Richey, Bailey Stewart, and Justin Peatross, Phys. Teach. 44, 460 (2006)
- Reflection on the study of flat mirrors: Two demonstrations, Jim Nelson, Phys. Teach. 22, 388 (1984)
INTRODUCTION: One of the basic concepts of optics in physics is the phenomenon of reflection, which allows us to understand how a ray of light behaves when it hits a material of any kind, such as mirrors, perspex and crystals, and of any form, i.e., flat, converging, convex, etc. In this experiment we will see how different light rays behave when they hit a flat mirror, which is the simplest example in optics.
OBJECTIVE: To verify the behaviour of a ray of light incident on a flat mirror.
MATERIALS: power source, leads, ray projector, sheets for multiple rays, graduated base, flat mirror.
SETUP: Use the leads to connect the ray projector to the power source so that the different sheets can then be introduced. Then, place a flat mirror on the graduated base and project the different rays onto it, while at the same time moving the mirror in a circular manner in both directions to observe the behaviour of the reflection.
EXPLANATION: On a flat mirror the refractive index is considered to be equal for both the first medium and the second one. Furthermore, because it is flat the mirror has a radius that can be considered as ∞. When a ray of light is incident on the mirror at a particular angle of incidence, i, it is reflected with an angle, r, given that the light returns to the first medium. This reflection can be considered as a refraction in which n=n’, which means we can conclude that the angles “r” and “i” are equal.
CONCEPTS: reflection, refraction, Snell’s Laws, Fermat’s Principle, incident ray, reflected ray, refractive index.
- P. Tipler, Física para la Ciencia y la tecnología, Reverté, 2012.
- F.W. Sears, M.W. Zemansky, H.D. Young y R.A. Freedman, Física universitaria, Pearson, 2012
- W.E. Gettys, F. Keller y M. Skove, Física clásica y moderna, McGraw-Hill, 2010.
STUDENTS 2012-2013: Luis Gandarela, Iago Blanco, Marina Pérez
LINK pdf STUDENTS (in Spanish):
STUDENTS 2012-2013: Julián Calle, Sergio Búa, Denis Barros.
LINK pdf STUDENTS (In Spanish) :