Science 8: Unit C – Light
and Optics
Topic 2: Reflection
What is Reflection?
• Reflection is the process when
a light ray strikes a surface and
bounces off it. Whenever light
rays strike an object, some of
them are reflected and some
are absorbed.
Two Types of Reflection
• Reflection occurs in
smoother surfaces
more than rougher
surfaces because
the light rays are all
reflected in the
same direction
where in a rougher
surface the light
rays are scattered in
all directions,
preventing an image
from forming.
Two Types of Reflection
Cont’d
• Regular/Specular
Reflection – Light
rays bounce off the
smooth surface at
the same angle.
• Rough/Diffuse
Reflection – Light
rays all bounce off
the rough surface
at different angles.
The Incident and Reflected
Rays and the Normal
• In reflection, the light ray
that approaches the surface
is called the incident ray
and the light ray moving
away from the surface is
called the reflected ray.
• A normal is an imaginary
line that is 90°
(perpendicular) to the
surface of the mirror. The
angle that the incident ray
makes with the normal is
called the angle of
incidence, and the angle
that the reflection ray
makes with the normal is
called the angle of
reflection.
The Law of Reflection
• The Law of Reflection – The
angle of incidence equals the
angle of reflection. This law
applies to all types of reflective
surfaces.
Concave Mirror
• A concave mirror is a
mirror whose
reflective surface
CAVES INWARDS. The
advantage of a
concave mirror is that
it helps focus the light
to a focal point,
producing an image
that can be put on a
screen. This image is
called a real image.
The downside of a
concave mirror is that
any object that is past
its focal point will be
upside down.
Convex Mirror
• A convex image is a mirror
whose reflective surface
bulges out. The advantage
of a convex image is that its
reflections are always rightside-up. Also you can see a
lot of your surroundings
with a convex image which
explains why they are used
in car mirrors and in
convenience stores. The
downside of a convex mirror
is that you cannot focus its
image on a screen. These
types of images are called
virtual images.
Attitude of an Image
• The attitude of
an image is
another word for
its orientation.
Is it upsidedown (inverted)
or right-side-up?
Concave vs. Convex
Images
• Mirror
• Draw its shape with
Reflective Surface
facing the left side.
• What type of image is
formed?
• Attitude of Image
formed?
• Can image formed be
larger than object?
• Concave
• )
• Real
• Usually
inverted
• Sometimes,
depending on
position of
object
• Can be put on a screen? • Yes
• Telescopes,
• Uses?
flashlights.
Convex
(
Virtual
Always right-side up
Always
smaller than object
No
Security and car
mirrors.