LIGHT : Mirrors
and Lenses
Mrs. Katrina F. Narnola
Reflection of Light
Definitions
• Luminous objects – generate their own
light (the sun)
• Illuminated objects – reflect light (the
moon)
• Line of Sight – a line from an object
or image to your eyes (light from the
object travels along this line to your
eyes)
Slide 4
Line of Sight
• Both luminous &
illuminated objects
emit/reflect light
in many directions.
• Your eye sees only
the very small
diverging cone of
rays that is coming
toward it.
Slide 5
Rays of Light
• Incident Ray –
leaves the object
and strikes the
mirror
• Reflected Ray –
leaves mirror and
strikes your eye
• The reflected ray is
on the line of sight
from the image to
your eye.
Slide 6
Law of Reflection
• Angle of incidence equals angle
of reflection.
Slide 7
Law of Reflection
• Normal – line
perpendicular to the
mirror surface
• Angle of incidence –
angle between incident
ray and normal
• Angle of reflection –
angle between
reflected ray and
normal
Slide 8
Law of Reflection Animation
i = r
Slide 9
Diffuse Reflection
Slide 10
Diffuse Reflection
Slide 11
Wet Road Glare
• Driving at night on a wet roadway results in
an annoying glare from oncoming
headlights.
Slide 12
Observing an Image
• An image is a position in
space from which all
reflected light appears
to diverge.
• Image formed by a plane
mirror is called a virtual
image.
• Virtual images are
formed in regions where
there is actually no light
Slide 13
Image Location
Slide 14
Image Formed By Plane Mirror
• Image is virtual.
• Image is located
as far behind
the mirror as
the object is in
front of the
mirror.
Slide 15
How Big Must the Mirror Be?
Slide 16
Distance from Mirror
Irrelevant
Slide 17
Right Angle Mirror
Slide 18
Right Angle Mirror
• Formation of
primary and
secondary
images
Slide 19
Kaleidoscope
• Angles smaller
than 90o
produce more
than 3 images
Slide 20
The Laws of Reflection:
There are two laws of reflection:
• The angle of incident ray is
equal to the angle of reflected ray.
• The angle between the normal
line and the reflected ray is the
angle of reflection.
Slide 21
Characteristics of images
formed by plane mirrors
• Image - virtual
• Orientation- erect
• Location - same distance from
the mirror as the object
distance
• Size - same size as the object
Slide 22
CURVED /
SPHERICAL
MIRRORS
Slide 23
Types of Curved Mirrors
• A concave mirror is called converging
mirror because the parallel incident
rays converge or meet/intersect at a
focal point.
Slide 25
Converging Mirror
• A series of flat
mirrors can be
arranged to reflect
parallel light through a
single point.
• Increasing the number
of flat mirrors causes
the shape to more
closely approximate a
parabola and causes
the reflected light to
converge in a smaller
area.
Convex Mirror
• It is a curved mirror in which the
reflective surface bulges towards the
light source.
• It is called Diverging Mirror because
the parallel incident rays diverge after
reflection. When extending the
reflected rays behind the mirror, the
rays converge at the focus behind the
mirror.
Slide 27
• A convex mirror is called diverging mirror
because the parallel incident rays diverge
after reflection. When extending the
reflected rays behind the mirror as
shown, the rays converge at the focus
behind the mirror.
Slide 28
• Center of Curvature “C”
- the center of the
sphere of which the
mirror is part, its
distance from the mirror
is known as the radius
Slide 29
Vertex “V”
- the center of the
mirror
Slide 30
Focal Point / Focus
- the point between the
center of curvature
and vertex, its distance
from the mirror is
known as the focal
length ,”f”
Slide 31
Slide 32
Slide 33
Concave Mirror Terms
• Axis
• Center of Curvature
• Radius of Curvature
• Focus
• Focal Length
