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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.
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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.