RAY MODEL OF
LIGHT
Predicting Behaviour of Light
• Underwater Photograph:
Q: Where is the Sun in the
diagram?
Q: What is the condition of
the surface water?
Q: What is the difference
between bright spots vs.
darker spots?
Ray Model of Light
• States that light is represented as straight
lines called rays, which shows the direction
that light travels.
• Rays end in arrows to show
travel direction.
• Light rays travel away from a
light source in every direction.
Brightness of Light
• Ray diagrams can explain brightness of light &
changes in distance
• More rays that reach your eyes, the brighter the
object & the closer light source is to you
Light rays hitting an object
• Ray diagrams can be used to explain what
happens when light strikes an object
• Materials are classified according to how
they react with light (3 types):
– Transparent materials
– Translucent materials
– Opaque materials
Types of Materials
• Transparent transmit light freely, absorbs &
reflect very little
• Translucent transmit some light, reflects little
• Opaque absorbs & reflects light, does not
transmit
Types of Shadows
• Ray diagrams explain size & location of
shadows (i.e. close vs. far)
• Shadow occurs when an opaque object
blocks light from a source
• Ex. shadow is
larger, if the object
is closer to light
source.
Types of Shadow
• Small light source sharp &
well-defined
• Wider the light source,
shadows more blurred
• Umbra: part of shadow where
all light rays are blocked
• Penumbra: partial shadow
created from non-point source
Solar Eclipse
• When moon is
located between
Earth & Sun
• Moon blocks light
coming from Sun
• You see the Moon as a
dark circle
Lunar Eclipse
• When Earth is located between Sun & Moon.
• Earth block’s sunlight that is normally reflected by
Moon.
• Sunlight is bent through our atmosphere
Moon has a coppery glow.
Light Reflection
• Incoming rays always travel parallel
• Smooth surface = Regular Reflection
• Light rays strike smooth surface & reflect in
same direction, staying parallel to one another
& reflected at same angle
• Possible to see an image in the reflection
Light Reflection
• Irregular surface = Diffuse Reflection
• Light rays strike rough surface will cause
light to scatter in different directions
• Ex. light is scattered by textbook, so you
can see page from almost any angle.
