Flat Mirrors Chapter 14 Section 2

Light and How It Travels  Light traveling through a uniform substance travels in a straight line. Air Water Vacuum Etc…  Once light encounters a different substance, its path will change. Air to water Vacuum to glass to air

Opaque  Opaque material is a substance that does not allow light to transmit through it. Most material is opaque.  Some of the light is absorbed by the material and the rest of it is deflected off the surface.

Reflection  Reflection – The turning back of an electromagnetic wave at the surface of a substance. Basically, a change in the direction of light.  Most materials absorb at least some of the incoming light and reflect the rest.  A mirror reflects almost all the light.

Reflection Depends Upon The Surface  The reflection of light depends upon the smoothness of the surface which the light is in contact with. Diffuse reflection is when light is reflected in many directions.  Paper, wood, cloth, etc.. Specular reflection is when the light is reflected all in the same direction.  Glass mirror, shiny metals, water.

Angles of Reflection  Incoming angles of light are equal to outgoing angles of light on a smooth surface.

Angle of Incidence  Angle of Incidence - The angle between a ray that strikes a surface and the normal to that surface at the point of contact. A line perpendicular to the reflecting surface is referred to as the “normal.”  Variable for Angle of Incidence θ (theta)

Angle of Reflection  Angle of Reflection – The angle formed by the line normal to a surface and the direction in which a reflected ray moves.  Variable for Angle of Reflection θ’ (theta prime)

Incidence and Reflection  The angle of incidence and angle of reflection are equal on a reflection surface. θ = θ’ Angle of incoming light ray = Angle of reflected light ray

Angle Between Light and Surface  The angle between the reflective surface and the incoming light ray equals 90º - θ.  The angle between the reflective surface and the reflected light ray equals 90º - θ’.

Flat Mirror  The simplest mirror is a flat mirror.  An object is placed a certain distance away from a mirror’s surface (p – object distance).  To an observer looking at the mirror, these rays appear to come from a location on the other side of the mirror (q – image distance)

Object Distance & Image Distance  The object distance and image distance are equal on a flat mirror.  Similarly, the image of the object is the same size as the object.

Virtual Image  Virtual Image – An image formed by light rays that only appear to intersect. Also known as an Imaginary Image.  A flat mirror always forms a virtual image, which can only be seen “behind” the surface of the mirror.  A virtual image can never be displayed on a physical surface.

Ray Diagrams  Ray diagrams are drawings that use simple geometry to locate an image formed by a mirror.

Ray Diagrams and Flat Mirrors  A ray diagram procedure will work for any object placed in front of a flat mirror.  The image formed by a flat mirror appears to have right-to-left reversal.

What Mirrors Don’t Do