JS 111: Physical Evidence Continuedand Basic Properties of Light

I. Pre-class activitiesA. Review- Quiz (and Physical Evidence below)B. Announcements- No Class next monday 6 Sept- Happy Labor Day!C. AssignmentsD. Measurements and errors

II. Physical Evidence Learning ObjectivesA. Define Physical Evidence B. Review proper CSI methods and documentation C. Review collection methodsDefine class vs individual characteristics

III. Basic Properties of Light Learning ObjectivesA. Define the properties of lightB. Define wavelength and frequency of lightC. Understand the basics of excitation and emission spectraSemen Detection Examples

IV. Team Fluorescent Applications

AssignmentsAssignment Due Weds 09/08/10- Required reading: Other references on fluorescence and semen detectionRead 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/en/home/References/Molecular-Probes-The-Handbook/Introduction-to-Fluorescence-Techniques.html

*Tutorial on Fluorescence and Fluorescent Instrumentation downloaded from http://fmrc.pulmcc.washington.edu/DOCUMENTS/FMRC299.pdf on 083010

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.

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.

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

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

• F=c/lambda

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

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- Beer’s Law- A=kc

• A= absorption c=concentration k=proportionality

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

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

Fluorescence microscopy permits the detection of cellular and molecular events using color

http://www.spectral-imaging.com/inner/fs_technology.html

Semen Detection Application

Semen Detection on Skin