Plane Mirror: a mirror with a flat surface Plane mirrors

create virtual images.A virtual image is a point at which light rays appear to diverge without doing so.

Image Point Source – point at which the object appears to be in the mirror from any vantage point in front of the mirror.

A similar cylinder can be placed behind a mirror to indicate the image point of the

cylinder placed in front of the mirror

The image formed by a plane mirror appears to be at a distance behind the mirror that is equal to the distance of the object in front of the mirror.

Converging Mirrors – A mirror where parallel light rays will intersect at a common point (focal point) upon reflection. Such mirrors are also referred to as a Concave Mirrors

Diverging Mirror – A mirror where parallel rays diverge upon reflection, as though the reflected rays come from a focal point behind the mirror. Such mirrors are also referred to as Convex Mirrors

Ray DiagramsThree types of rays used to

find the location and magnitude of an imageParallel Ray is a ray that is incident along a path parallel

to the optic axis and is reflected through the focal point

Chief Ray or Radial Ray is a ray incident through the center of curvature (C). Since it is incident normal to the mirror’s surface, this ray is reflected back along its incident path, through C.

Focal Ray is a ray that passes through the focal point and is reflected parallel to the optic axisC = 2f

C is the center of curvature

f is the focal length

F is the focal point

Focal Point

A Focal Point is a point location where parallel rays that are

reflected from a mirror meet.

Images Formed with Concave Mirrors

Parallel Ray and Focal Ray are needed to determine the

location and size of object.

Images Formed with Concave Mirrors

When object Beyond C:

Image is

Real

Inverted

Smaller

do > di

ho > hi

Images Formed with Concave Mirrors

When object is at C

Image is

Real

Inverted

Same Size

do = di

ho = hi

Images Formed with Concave Mirrors

When object is between C and F

Image is

Real

Inverted

Larger

do < di

ho < hi

Images Formed with Concave Mirrors

When object is at F

No Image

Images Formed with Concave Mirrors

When object is between F and Mirror

Image is

Virtual

Erect

Larger

do < di

ho < hi

Object Location

OverviewObject

Object

Image

Image

Convex Mirrors and Images

All Images are

Virtual

Erect

Smaller

do > di

ho > hi

Mirror Equations

f = Focal Distance

do = Object Distance

di = Image Distance

M = Magnification

hi = Height of Image

ho = Height of Object

dd f

d fio

o

A more useful Equation

The focal length f is positive for concave mirrors and negative for convex mirrorsThe object distance do is always positive

The image distance di is always positive for a real image (same side of mirror as object) and negative for a virtual image (forms behind the mirror)The magnification M is positive for an upright image and negative for an inverted image

Signs

for

Common to find image location