JS 111: Physical Evidence Continued and Basic Properties of Light

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JS 111 Physical Evidence Continuedand Basic
Properties of Light

• Pre-class activities
• Review- Quiz (and Physical Evidence below)
• Announcements- No Class next monday 6 Sept- Happy
  Labor Day!
• Assignments
• Measurements and errors
• II. Physical Evidence Learning Objectives
• Define Physical Evidence
• Review proper CSI methods and documentation
• Review collection methods
• Define class vs individual characteristics
• III. Basic Properties of Light Learning
  Objectives
• Define the properties of light
• Define wavelength and frequency of light
• Understand the basics of excitation and emission
  spectra
• Semen Detection Examples
• IV. Team Fluorescent Applications

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Assignments
Assignment Due Weds 09/08/10- Required reading
Other references on fluorescence and semen
detection Read Chapter 1 in the book.- Pages
1-19. Read the following 2 articles. Write a 3
page summary, 3 questions and 3 answers. Submit
by email to Lee by 09/08/10 1200 noon. Bring hard
copy to class weds 090810. Introduction to
fluorescence- http//www.invitrogen.com/site/us/e
n/home/References/Molecular-Probes-The-Handbook/In
troduction-to-Fluorescence-Techniques.html Tutor
ial on Fluorescence and Fluorescent
Instrumentation downloaded from
http//fmrc.pulmcc.washington.edu/DOCUMENTS/FMRC29
9.pdf on 083010
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CSI Exercise 1- Measurements and Documentation

• In your small teams using the rulers you have
  been provided, measure to the nearest 0.1 mm the
  object for your team.
• Team leaders should collect all measurements on
  one paper. Write down the range of measurements
  (eg 10.3-10.7mm) and calculate the average
  measurement.
• In addition, take measurements to document the
  location of the object.
• Once completed be sure everyone signs the paper
  and hand it in.

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CSI Measurement Questions

• Did you all agree on the measurements?
• If no, what are 3 reasons which may cause the
  discrepancy? (what are variables in
  measurements?... what might we encounter in the
  use of fluor measurements?)
• For one of the reasons, design an experiment to
  test your hypothesis.
• Is there enough documentation for you to
  reconstruct the location of the object.

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Theory of Light-1See http//micro.magnet.fsu.edu/
primer/lightandcolor/index.html for additional
information and review

• White light is composed of a range of colors
• ROYGBIV
• Red glass absorbs all component colors except red
  passing through or transmitted
• Color is a visual indication of an objects
  ability to absorbing some and reflect other
  components of visible light

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Theory of Light -2

• Light described as continuous wave or stream of
  discrete energy particles
• Light as a wave in up and down motions has
  wavelength (lambda-) in nanometers
• The frequency is the number of crests per unit
  time
• Speed of light is 300 million m/s- symbol c
• Frequency and wavelength are inversely
  proportional
• Fc/lambda

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Theory of Light-3

• Visible light is only a small part of the entire
  electromagnetic spectrum
• Normal light is a collection of waves possessing
  a range of wavelengths and are out of step with
  each other
• When pulsating in unison they are coherent or
  laser Light amplification by the simulated
  emission of radiation

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Theory of Light-4

• Absorption of Electromagnetic Radiation
• Any substance exhibit selective absorption of
  electromagnetic radiation
• Different materials have different absorptions
• The selective absorption of a substance is
  measured by an instrument called a
  spectrophotometer.
• It produces an absorption spectrum depicting the
  absorption of light as a function of wavelength
  or frequency. Absorption of UV, visible and IR
  are particularly applicable for identification of
  organic substances- How much- Beers Law- Akc
• A absorption cconcentration kproportionality

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Spectrophotometer

• Instrument used to measure and record the
  absorption spectrum of a chemical substance
• Components- 1. Radiation source
• 1- Radiation source (UV, vis, IR)
• 2. Monochromator or frequency selector
• 3. Sample holder
• 4. Detection to convert electromagnetic radiation
  into an electric signal (digitizer)
• 5. Recorder

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Spectrum

• Different materials may have distinctively
  different absorption spectra
• Each spectrum may have distributions that are
  different from others or may share
  characteristics similar to other compounds

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Fluorescence microscopy permits the detection of
cellular and molecular events using color
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http//www.spectral-imaging.com/inner/fs_technolog
y.html
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Semen Detection Application
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Semen Detection on Skin