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