2. What is a mirror?
an object that reflects an image
a wave reflector
Reflection – bouncing
of light rays when it
hits a surface
3. Types of Mirrors
Plane Mirror
- a mirror with a flat
reflective surface
Spherical Mirror
- has the shape of a piece
cut out of a spherical
surface
4. Light Rays
Light ray is an idealized model of light, which is drawn
as a straight line.
Incident Ray (i) – the ray of light approaching a
surface of a mirror
Reflected Ray (r) – the ray of light which leaves the
surface of the mirror
Normal line (n) – an imaginary line that can be drawn
perpendicular to the surface of a mirror at the point of
incidence where the ray strike in the mirror
6. i r
n
𝜃𝑖 𝜃𝑟
Angle of incidence (𝜃𝑖)
– the angle between
the incident ray and
normal line.
Angle of incidence (𝜃𝑟)
– the angle between
the reflected ray and
normal line.
7. i r
n
𝜃𝑖 𝜃𝑟
The Angle of incidence
(𝜃𝑖) is equal to the
Angle of incidence (𝜃𝑟).
𝜃𝑖 = 𝜃𝑟
∠𝑖 = ∠𝑟
Law of Reflection
The normal line, incident ray, and the reflected ray
lie on the same plane.
8. Reflection of Light
Specular/Regular Reflection
◦ light is reflected from a
smooth surface at a definite
angle
Diffused/Irregular Reflection
◦ produced by rough surfaces
that tend to reflect light in
all directions
9. Reflection of Light
Specular/Regular Reflection
◦ light is reflected from a
smooth surface at a definite
angle
Diffused/Irregular Reflection
◦ produced by rough surfaces
that tend to reflect light in
all directions
10. Reflection in a Plane Mirror
Characteristics of images
formed by a plane mirror:
1. Image is virtual;
2. Same size as the object;
3. Same orientation as the
object; and
4. Same distance from the
mirror as the object.
12. Reflection in Spherical Mirrors
Concave Mirror
reflects light inward to one
focal point
used to focus light.
also known as converging mirror
has a reflecting surface that is
recessed inward (away from the
incident light)
13. Reflection in Spherical Mirrors
Concave Mirror
reflects light inward to one
focal point
used to focus light.
also known as converging mirror
has a reflecting surface that is
recessed inward (away from the
incident light)
14. Reflection in Spherical Mirrors
Convex Mirror
also known diverging mirror
a curved mirror in which the
reflective surface bulges
towards the light source
reflect light outwards;
therefore they are not used
to focus light
15. Reflection in Spherical Mirrors
Convex Mirror
also known diverging mirror
a curved mirror in which the
reflective surface bulges
towards the light source
reflect light outwards;
therefore they are not used
to focus light
16. Types of Images Formed in Reflecting
Surfaces
REAL IMAGE
1. A real image is formed when light
rays actually meet after reflection.
2. A real image can be formed on a
screen.
3. A real image is inverted with
respect to the object.
VIRTUAL IMAGE
1. A virtual image is formed when
light rays do not actually intersect
after reflection, but they appear to
diverge from the mirror.
2. A virtual image cannot be formed
on a screen.
3. A virtual image is erect with
respect to the object.
17. Types of Images Formed in Reflecting
Surfaces
REAL IMAGE VIRTUAL IMAGE
18. Types of Images Formed in Reflecting Surfaces
Image Real
(formed when
rays converge)
Virtual
(formed when
rays diverge)
Orientation Upright
(right side up)
Inverted
(upside down)
Location Depends on the object location
Size
magnification
(ratio of the image
dimensions to the
object dimensions)
Larger >1 Smaller <1 Same 1
19. Magnification Equation
tells the change in size or height of the image relative to the object and
image distance of the mirror
𝑴 =
𝒉𝒊
𝒉𝒐
= −
𝒅𝒊
𝒅𝒐
where: M = the magnification (no unit)
𝒉𝒊 = height of the image 𝒅𝒊 = distance of the image
𝒉𝒐 = height of the object 𝒅𝒐 = distance of the object
Note: The height of the image (𝒉𝒊) will be negative if the
image is inverted or real.
20. Sample Problem 1:
An object 11cm tall is 9cm from a
mirror. If the image distance is -3cm
from the mirror, what is the image
height?
21. Sample Problem 2:
A candle is 14.7cm tall, and the
image is 21.9cm tall. What is the
magnification of the mirror?
22. Sample Problem 3:
The image produced by a concave
mirror is at -16.2m, and the
magnification is 1.79. What is the
object distance?
23. “The mirror is my
best friend
because when I
cry, it never
laughs.”
~ Charles Chaplin
