Transcript Light Continued

Light Continued
The light models explain how we…
• See ____________
distant objects
apparent bends in objects
• See ______________
• ______
Can’t see around corners
shadows
• See ________
How do we see things?
• Light travels in ________
straight lines:
Laser
• We see things because they
reflect light into our eyes:
________
Astronomy
Part 2 - Reflection
• Reflection from a mirror:
Normal
Reflected ray
Incident ray
Angle of
incidence
Angle of
reflection
Mirror
• The Law of Reflection
Angle of incidence = Angle of reflection
In other words, light gets reflected from a surface at
the same angle it hits it.
The
same !!!
Clear vs. Diffuse Reflection
• Smooth, shiny
surfaces have a clear
reflection:
Rough, dull surfaces have
a diffuse reflection.
Diffuse reflection is when
light is scattered in
different directions
Color
• White light is not a single color; it is
made up of a mixture of the seven
colors of the rainbow.
We can
demonstrate
this by splitting
white light with
a prism:
Seeing color
• The color an object appears
depends on the colors of light it
______.
reflects
White
light
Only red light
is reflected
Refraction
Refraction is when waves bend or
_________
change speed due to travelling in a
different medium.
medium is something that waves
A _______
will travel through.
• Shadows
Shadows are places where light is
blocked
“_______”:
Rays of
light
Shadow(s)
• Light from a
single
direction.
• Sun-light.
– Has one shadow
• Two light sources
– Two shadows
Life of a Photon – 4 Steps
•
•
________
Emitted - released
___________
Transmitted – pass through an
object
–Air, glass, water, plastic, space
• _____________
Bounce/Scatter – reflect off surface
of objects
• ________
Absorbed – ultimately photons strike
an object and disappear
How light or electromagnetic
radiation is used in Astronomy
• Astronomers use a tool called a
spectroscope to separate starlight into
its colors – in this way, they can tell
what a star is made of, its temperature,
luminosity and so on…
• Astronomers can look at astronomical
objects at different wavelengths…