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Chapter 4
Spectroscopy Part 2
•Spectroscopy is the study of the energy which is given off and
absorbed when atoms go from the ground state to the excited
state and back again.
•Spectroscopy is often used in chemistry for the identification of
substances, through the spectrum absorbed or emitted.
Neon Signs
Light Sources – Mercury
Mercury Vapor Lamp
The average rated life of a CFL is between 8
and 15 times that of incandescents. CFLs
typically have a rated lifespan of
between 6,000 and 15,000 hours,
whereas incandescent lamps are usually
manufactured to have a lifespan of 750
hours or 1,000 hours.
• Spectrum of a CFL bulb. The camera
had a diffraction grating in front of
the lens. The discrete images are
produced by the different colors in
the light, a line spectrum. An
incandescent lamp would instead
have a continuous band of color.
American and 2 Japanese Physicists Share 2014
Nobel Prize for Work on LED Lights
• LEDs, (Light emitting diodes), are found
in all kinds of devices.
• They form numbers on digital clocks,
transmit information from remote
controls, light up watches.
• Collected together, they form the
illuminated screens on cell phones and
television screens.
• Basically, LEDs are just tiny light bulbs
that fit easily into an electrical circuit.
But unlike ordinary incandescent bulbs,
they don't have a filament that will burn
out, and they don't get especially hot.
• LED’s are illuminated solely by the movement
of electrons.
• The lifespan of an LED is impressive lasting
10 times as long as a fluorescent bulb and 100
times as long as an incandescent bulb.
• LED bulbs do not have toxic mercury as do
• Due to low power requirements, it can be
powered by cheap local solar power. Thus
bringing the advantage of electrical devices to
places that lack electrical power grids.
• Currently upfront costs are higher than many
consumers which to pay but costs are
continuing to drop as technology improves.
• In the future, some of the most incredible uses of LEDs will
actually come from organic light emitting diodes, or OLEDs
which are flexible, allowing scientists to create bendable lights
and displays. (Imagine rolling your TV up like a poster and
carrying it with you anywhere).
• You'll find them in
everything from CD
players to dental drills
to high-speed metal
cutting machines to
measuring systems.
Tattoo removal, hair
replacement, eye
surgery -- they all use
Flame Tests
Flame Tests
• A flame test is a procedure used in chemistry to detect
the presence of certain metal ions based on each
element's characteristic emission spectrum.
Video: Flame Tests (27seconds)
..\..\..\..\Videos\Flame Tests.wmv
Video: Molecular Fingerprints (15 min.)
Worksheet is in notebook.
• ..\..\..\..\Videos\World of
Chemistry\Molecular Fingerprints.mpg
Homework Due Tomorrow
• Lab Summary: “Flame Tests”.
• Chapter 4 Worksheet 3.
• Study Guide Chapter 4.