Reflection: Angle Law, Surface Types, Mirror Images, and Retroreflectors

All flashcards

State the law of reflection.

The angle of reflection equals the angle of incidence, or $\theta_r = \theta_i$. Both angles are measured from the normal to the surface.

What is diffuse reflection?

Diffuse reflection occurs when light reflects from a rough surface and spreads in many directions because the surface’s small regions have differently oriented normals.

How far behind a plane mirror does an image appear?

The image appears the same distance behind the mirror as the object is in front of it. The image is virtual because the rays only appear to come from behind the mirror.

What does a corner reflector do to a light ray?

Two mutually perpendicular reflecting surfaces send a ray back parallel to its original direction, independent of its angle of incidence.

What is a practical use of retroreflectors?

Bicycle and vehicle reflectors return headlight light toward drivers, helping make the objects visible when the observer is near the light source.

Quiz questions

1. What relationship does the law of reflection specify between the angles of incidence and reflection?Answer: The angles are equal: $\theta_r = \theta_i$.
2. From which reference line are the angles of incidence and reflection measured?Answer: From the normal, perpendicular to the surface at the point of incidence.
3. Why can a sheet of paper be seen from many different viewing angles?Answer: Its differently oriented surface regions reflect light in many directions.
4. You stand $2\,\text{m}$ in front of a plane mirror. Where does your image appear?Answer: $2\,\text{m}$ behind the mirror.
5. Why do bicycle reflectors help drivers see a bicycle when headlights shine on it?Answer: They return much of the light toward the direction it came from.