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With
Curved
Mirrors
Created by Derek J. Wells. Under the expressed written consent of Derek J. Wells in
accordance with the rules and by-laws of Derek J. Wells. All events depicted here are
fictional. Any similarity to real life situations are merely coincidental.
Types of Mirrors
The everyday flat type of mirror is called a “plane mirror”. All light traveling
straight towards this mirror reflects right back at you. As such, you always get an
image that is an exact duplicate of you. Remember, MIRRORS REFLECT
LIGHT, so it bounces off them. This may seem silly in that we already know that,
but as we talk of more optical instruments its something you should keep in mind.
Curved mirrors are not flat and therefore light reflects differently off
them making different types of images. There are two types of curved
mirrors
A concave mirror.
And
This mirror has a
concave shape when
looking at it from
the left side.
This mirror looks like a
“cave” if you were
walking into it from the
left side.
A convex mirror
This mirror has a
convex shape when
looking at it from
the left side
The concave mirror is also called a converging mirror because it causes horizontal light
rays to converge (come together) when they reflect off the mirror
The convex mirror is also called a diverging mirror because it causes horizontal
light rays to diverge (move apart) when they reflect off the mirror
Terminology
Curved mirrors are approximated to
have a circular shape.
We can make a curved mirror by cutting part of
mirrored circle out.
The mirror was cut
from a circle.
Terminology
The center of the circle that the
mirror is part of is point C.
Point C is called:
C= Center of Curvature
C
R
The radius of the circle
that the mirror is part of is
distance R
Distance R is called:
R= Radius of Curvature
Terminology
C
Principle Axis = The
horizontal line drawn through
the center
f
f = Focal point (of a concave mirror)
= the point through which all
reflected rays bouncing off the
mirror CONVERGE
f
f = Focal point (of convex mirror)
= the point at which all reflected
rays APPEAR to come from when
they reflect
The focal point(f) is 1/2 of the distance to the center of curvature point
(C)
f = R / 2
C
Terminology
Distance object is
placed from the mirror
Also
ho = object height
d0
hi = image height
An object
placed
near a
mirror
C
f
f
C
di
Front Side of
Mirror
(the real side)
When images are formed on the
front side of the mirror they are
real images. Real images can be
projected onto a screen.
Distance image
is formed from
the mirror
The image of
the object that
is produced by
the mirror
Back Side of Mirror
(the virtual side)
When images are formed on the back
side of the mirror they are
images.
virtual
Curved Mirrors
Concave mirrors can
form any types of these
images:
Convex mirrors can
only form one type of
image ALWAYS:
- real or virtual
- virtual
- smaller, same size, or
larger
- real images are
ALWAYS inverted or
upside down
- smaller
- upright
Important - when using a convex
mirror the focal point (f) must
be negative (-) because it is
behind the mirror
Ray Diagrams (for concave mirrors)
The FIRST incident light ray we
draw goes horizontally straight
towards the mirror (Parallel)
C
This light ray reflects back
and passes through the focal
point (Focal)
f
Ray Diagrams (for concave mirrors)
The second incident light ray we
draw goes through the focal point
before it hits the mirror
C
This light ray reflects back
parallel to the optical axis
f
Putting it all together.
Draw both rays, and the point where they
intersect or converge represents the point
where the tip of the image will be formed
BEYOND C...
Image
C
f
Describe the image
(LOST):
L = Closer
O = Inverted
S = Smaller
T = Real
L = location of image compared to actual object
O = Orientation of Image
S = Size of Image
T = Type of Image
Special Examples
1- When the object is located exactly on (f) the rays will not intersect anywhere and
there will be no image
2- When the object is placed right on C, the REAL image is inverted and the same size
At C...
C
Image
f
Describe the image:
L = same
O = inverted
S = same
T = real
Special Examples
3 - When the object is placed in front of f...
Inside F...
Notice that these rays do
not intersect anywhere
over here
C
We extend the
reflected rays back
behind the mirror
to see where they
appear to come
from. This is the
image point.
Image
f
Describe the image:
L = farther
O = upright
S = Larger
T = Virtual
Ray Diagrams (for
convex mirrors)
The nice thing about Convex mirrors is that the ray diagrams are ALWAYS,
ALWAYS the same. They are slightly different then the concave mirrors
however and you should be careful to notice the differences. In this type of
mirror, you always have to extend the reflected rays back behind to find the
image
For example...
f
C
Ray Diagrams (for convex mirrors)
f
C
The first light ray is:
Parallel, then focal
This light ray reflects back
AS IF it came from point “f”
Ray Diagrams (for convex mirrors)
The second light ray is:
Focal, then parallel
f
C
This light ray reflects back
horizontally (parallel)
Ray Diagrams (for convex mirrors)
Put them all together and extend the reflected rays behind the mirror to find
the object
Notice that these
rays do not intersect
anywhere over here
Describe the image:
L = closer
O = upright
S = smaller
T = Virtual
We extend the reflected
rays back behind the
mirror to see where they
appear to come from.
This is the image point.
Image
f
C