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Chapter 4 (8)
Light and Optical Systems
Light behaves in predictable ways
Text book pages 92-95
Do 7.1 – 7.3 in your
workbooks
Light Interaction
• Depending on the
situation, light will
reflect, absorb and
transmit at or
through objects.
• Remember that light
travels in straight
lines from objects to
your eyes.
• Ray diagrams can help
Ray Diagrams
• Ray diagrams are used
to show how light
travels.
• Light traveling from a
source is shown as a
straight line called a
ray.
explain why the
brightness or
intensity of light
changes with distance.
• Ray diagrams also
help to explain
shadows. A lack of
light is considered to
be a shadow.
Ray Diagrams
• Light hits an object
and is reflected to the
eye thereby producing
an image of the
object.
Light Interacts
With Materials
From air into water or
glass
• When light hits an
object, it behaves in
different ways
depending on they
type of the material
each object is made of.
• Transparent materials
can transmit light – it
passes right through
them.
• Eg. Glass, clear plastic
Other types of materials that light
comes into contact with
• Translucent – allow some, but
not all, light to pass through.
Eg. Frosted window pane.
• Opaque – do not let any light
through. They absorb or reflect
the light. Shadows are created
as light passes in front of these
materials. Eg. Brick, wood,
metal.
Other Types of Materials
• Non-Luminous – they
do not produce light.
Also includes opaque
objects.
• Luminous – a light
source. Eg. Lamp, the
sun, fire.
Types of Reflection: Regular Reflection
• Regular Reflection –
light rays hit a
smooth surface.
• Light rays are
parallel to each
other.
• Reflected at same
angle.
• Produce clear image.
Types of Reflection:
Diffuse Reflection
• Diffuse Reflection – when
light rays strike a rough or
uneven surface.
• Reflected at a different
angle.
• Rays do not remain parallel.
• Scatter the light rays.
• Can see objects from many
positions.
The Law of Reflection
• Incident Rays – are the incoming rays of light.
• The shinier and smoother the surface the better
the reflection.
• Plane Mirrors – flat mirrors – will allow for the
clearest of reflections
The Law of Reflection
 When a ray of light hits a plane mirror at an angle, it
bounces off the mirror surface at exactly the same
angle.
 The “Normal” – a line perpendicular to the mirror at
the point of reflection
 Angle of incidence – the angle between the incident
ray and the normal
 Angle of reflection – the angle between the reflected
ray and the normal.
The Law of Reflection cont…
• THE LAW OF
REFLECTION – the
angle of incidence is
equal to the angle of
reflection.