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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
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