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