Science Starter: March 5, 2012Write out the definition and
match the correct term in your science notebook.2) How a light wave
bens when it enters a new medium at an angle3) How a light wave
bounces back when it hits a barrier4) The type of wave visible
light isElectromagnetic Wave RefractionReflection
SpectrumMechanical Wave Radiation
Science Starter: March 6, 2012Write the question and correct
answer in your science notebook4) An EM wave is caused by a
disturbance in a. The atmosphere b. A material medium c. A field5)
In a vacuum, the speed of EM waves a. Always remains constant b.
Decreases as the waves spread out c. Depends on the source of the
wave
Light Sources and Interactions
Facts about Visible Light Light is the only form of EM
radiation for which humans have specialized sensory organ. The
human eye is very sensitive to light and color Most living
creatures depend on visible light for their survival.
Incandescence The Suns high temperature produces light of every
wavelength. Incandescence- the production of light by materials at
high temperatures Example: sun, lightening, fire, incandescent
light bulbs
Living Things Produce Light Luminescence- the production of
light without high temperatures Bioluminescence- the production of
light by living organisms Light is created with a chemical process
rather than intense heat
Human Technology Produces Light Incandescent Light Bulbs- uses
a glass bulb and a tungsten filament Halogen Light Bulbs- used a
quartz bulb, tungsten filament, and a halogen gas mixture
Fluorescent Light Bulbs- uses phosphor coating, electrical current,
mercury vapor and other gases.
Fluorescent and LED Lights Fluorescence- occurs when a material
absorbs EM radiation of one wavelength and gives off EM radiation
of another Light emitting diode (LED)- a semiconductor that
converts electric energy directly into light Advantages of LED:
produce brighter light, do not break, uses little energy and heat,
can last for decades
Light Waves Interact with Materials Transmission- the passage
of an EM wave through a medium Transparent- materials that allow
most of the light that strikes to pass through Translucent-
materials that transmit some light, but they also cause it to
spread out in all directions Opaque- materials that do not allow
any light to pass through
Light Waves Interact with Materials Absorption- the
disappearance of an EM wave into the medium. Absorption affects how
things look, because it limits the light available to be reflected
or transmitted.
Light Waves Interact with Materials Scattering- the spreading
out of light rays in all directions, because particles reflect and
absorb the light.
Light Waves Interact with Materials Polarization- quality of
light in which all of its waves vibrate in the same direction
Wavelengths Determine Color When all wavelengths of visible
light are present the light will appear white. A prism is a tool
that uses refraction to spread out the different wavelengths that
make up white light.
Color Reflection and Absorption The color of an object or
material is determine by the wavelength it absorbs and
reflects.
Primary Colors of Light The human eye detects three color
bands: red, green and blue. When all colors are mixed together you
perceive white light