Properties of Reflective Waves
Curved Mirrors
Image close to a concave mirror
appear:
Larger than the object
Upright
Image far from a concave mirror
appear:
Smaller than the object
Inverted or upside down
Another factor that influence
image appearance is:
Curvature
R = radius of curvature or/ radius of the
spherical mirror
C = center of curvature of the mirror
Another factor that influence
image appearance is:
Curvature
R = radius of curvature or/ radius of the
spherical mirror
C = center of curvature of the mirror
Image location can be found using
the mirror equation:
(1/p) + (1/q) = (2/r)
Two kinds of images
Real- images that form in
front of the mirror
Virtual- images that form
behind the mirror
The FOCAL POINT (F) is half way
between the center of curvature
and the mirrors surface
The distance to the focal point is
the focal length (f)
(1/p) + (1/q) = (1/f)
Real images form on the front side
of the mirror
Virtual images form on the back
side of the mirror
The mirror is drawn so the front
side is on the left
Positive numbers indicate the front
side of the mirror
Negative numbers indicate the
back side of the mirror
The principal axis runs through the
center of the mirror
Positive numbers are above the
principal axis
Negative numbers are below the
principal axis
The measure of the image
compared to the object
M- magnification
M= (h`/h) = -(q/p)m
M is positive means the image is
upright
M is negative means the image is
inverted
1. Parallel to principal axis –
through focal point F
2. Through focal point F –
parallel to principal axis
3. Through center of
curvature C – back along C
A concave makeup mirror is
designed so that a person 25.0
cm in front of it sees an upright
image at a distance of 50.0 cm
behind the mirror. What is the
radius of curvature? What is the
magnification? Is it real or
virtual?
A concave shaving mirror has a focal
length of 33cm. Calculate the image
position of a cologne bottle placed
in front of the mirror at a distance
of 93 cm. Calculate the
magnification of the image. Is it real
or virtual, upright or inverted? Draw
a ray diagram.
A pen is placed 11.0 cm from a concave
mirror produces a real image 13.2
cm from the mirror. What is the
focal length? What is the
magnification of the image? If the
pen is placed 27.0 cm from the
mirror, what is the new position of
the image? What is the
magnification? Is it real or virtual?
Where do we see convex
mirrors?
Diverging mirrors
Image is always virtual or a
negative number
Focal point and center of curvature
are always behind the mirror
See page 538
Table 14-4
A convex mirror with a radius of
curvature of 0.550 cm is placed
above the aisles in a store.
Determine the image distance and
magnification of a customer lying
on the floor 3.1 m below the mirror.
Is the image real or virtual, upright
or inverted?
A spherical glass ornament is 6.00 cm in
diameter. If an object is placed 10.5
cm away from the ornament, where
will its image form? What is the
magnification? Is the image real or
virtual, upright or inverted? Draw a
ray diagram.
A soda bottle is placed 44cm from a
convex mirror. If the mirror’s focal
length is 33 cm how far from the
mirror’s surfaced does the bottle’s
image form? What is the
magnification? Is the image real or
virtual, upright or inverted? Draw a
ray diagram.
When light rays do not intersect at
a unified point, the observer will
see a blurred image
SPHERICAL ABERRATION
To eliminate spherical aberration:
Use mirrors with small
diameters
Use parabolic mirrors
Segments of a Paraboloid (three
dimensional parabola)
All rays parallel to the principal axis
converge at the focal point
Where do we use Parabolic
Mirrors?
Two types of telescopes
Refracting – combination of
lenses
Reflecting – uses curved lenses
and small mirrors
Parabolic mirror (objective mirror)
used to focus light