Transcript What Wavelength Was That?

5.3 Light
How do you LIGHT UP
your world ?
Welcome to a power point
presentation on LIGHT.
• We will investigate the following:
• 1. What is light?
• 2.What are some sources of light around us?
• 3. What are opaque, transparent, & translucent
objects?
• 4. What is a light wave?
Light
• Our primary source of light is the sun.
• Light travels in straight lines at a speed of
186,000miles per second.
• *Light waves travel faster than sound waves!
• Light energy from the sun travels through
space , reaches earth, and some of it turns to
heat energy and warms the earth’s air.
• Light from the sun also travels to the cells of
green plants (producers) and is stored as
energy.
• When light reaches an object, it is absorbed,
reflected, or passes through it.
How many sources of Light
can you list and explain?
“Just Passing Through:”
What happens when light strikes
glass? Or waxed paper? Or a book?
• If light travels through an
object it is =transparent
• If light is blocked by an
object and a dark
shadow is cast it is=
opaque.
• If some light passes
through but not all and a
light shadow is present it
is=translucent.
What happens when light
hits these objects?
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Glass of water
School bus window
Notebook paper
Waxed paper
Plastic wrap
Tissue paper
Cardboard
Textbook
Hand lens…
Transparent objects:
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The windows on a school bus,
A clear empty glass,
A clear window pane,
The lenses of some eyeglasses,
Clear plastic wrap,
The glass on a clock,
A hand lens,
Colored glass…
ALL of these are transparent.
Yes, we can see through them
because light passes through
each of them.
Translucent objects
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Thin tissue paper,
Waxed paper,
Tinted car windows,
Frosted glass,
Clouds,
All of these materials
are translucent and
allow some light to
pass but the light
cannot be clearly
seen through.
Opaque objects:
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Heavy weight paper,
Cardboard
Aluminum foil,
Mirror, bricks, buildings,
Your eyelids and hands,
Solid wood door,
All of these objects are
opaque because light
cannot pass through them
at all.
• They cast a dark shadow.
What is light really?
• Light waves are three
dimensional.
• Light waves vibrate in all
planes around a center
line.
• The waves have high
points called “crests.”
• Waves also have low
points called “troughs.”
• *The distance from one
crest to the next crest is
called a “wavelength.”
• *The number of waves
passing a given point in
one second is called the
“frequency.”
wavelength
Don’t’ forget…longest waves (radio) ..to shortest waves (cosmic)
Radio
(Longest electromagnetic waves)
• Emitted by
– Astronomical Objects
– Radio Station
Transmitters
• Detected by
– Ground based radio
telescopes
– *If you turn on a radio,, it
will convert the radio
wave energy into sound
energy.
Television
• Shorter than radio,
also used to carry
messages (pictures
& sound) to our TV
sets.
• *We can sense the
TV waves around us
with our televisions.
Microwave
• Emitted by:
– Gas clouds collapsing
into stars
– Microwave Ovens
– Radar Stations
– Cell Phones
• Detected by
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Microwave Telescopes
Food (heated)
Cell phones
Radar (systems)
Infrared
(Heat or Thermal)
Are you a source of infrared? YES you are!
• Emitted by
– Sun and stars (Near)
– TV Remote Controls
– Food Warming Lights
(Thermal)
– *Everything at room
temperature or
above,=HEAT
• Detected by
– Infrared Cameras
– TVs, VCRs,
– Your skin
Visible
Each color is a different size wave.
Red the longest & violet the shortest
• Emitted by
– The sun and other
astronomical objects
– Laser pointers
– Light bulbs
• Detected by
– Cameras
(film or digital)
– Human eyes
– Plants (red light)
– Telescopes
Ultraviolet
Sunburn / black light
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The sun
Tanning booths
Black light bulbs
UV lamps
• Detected by
– Space based UV
detectors
– UV Cameras
– Flying insects (flies)
• Emitted by
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X-ray
Astronomical objects
X-ray machines
CAT scan machines
Older televisions
Radioactive minerals
Airport luggage
scanners
• Detected by
– Space based X-ray
detectors
– X-ray film
– CCD detectors
Gamma Ray
• Emitted by
– Radioactive materials
– Exploding nuclear
weapons
– Gamma-ray bursts
– Solar flares
• Detected by
• --Geiger counters
– Gamma detectors and
astronomical satellites
– Medical imaging detectors
COSMIC Rays
(The highest energy waves and the deadliest)
• Cosmic rays come
from deep space and
can pass through the
Earth.
Lewis Latimer
• African-American
• Lived from 1848-1928
• Invented a long-lasting carbon filament
that made the light bulb more useful.
• He also patented a threaded wooden
socket for light bulbs and supervised the
installation of electric streetlights in New
York City, Philadelphia, Montreal, and
London.
Isaac Newton
• English
• Lived from 1643-1727
• Discovered that white light was not a
simple entity, but splits into a range of
colors
• When he passed white light through a
glass prism, he noted that a spectrum of
light was formed; particle theory of light
• Reflecting telescope
Anton van Leeuwenhoek
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Dutch; born in Holland
Lived 1632-1723
Made over 500 simple microscopes
Discovered bacteria, free-living and
parasitic microscopic protists
Galileo Galilei
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Italian
Lived from 1564-1642
Developed the refracting telescope
Developed the first known example of the
microscope
Robert Hooke
• English
• Lived from 1635-1703
• Devised the compound microscope and
illumination system
• Discovered plant cells
• Examined fossils with a microscope