1. Chapter 5: Light and Matter Spectrophotometry
Forensic Science
Ms. Urling

2. Electromagnetic Radiation
Energy in the form of waves
Some light energy is visible to humans as color

3. Waves What is? What happens to the frequency as wavelength increases?
What else travels as waves?

4. EM Radiation and Forensics
Infrared, UV, and visible light can be used to identify drugs, inks, explosives, fibers, paints, skeletal remains, paintings, etc.
Bone fluoresces under UV light.
UV radiation can be used to find bones at night.

5. Spectrophotometer Spectrophotometer
spectro = spectrum (range)
photo = color
meter = measurement
Measures which frequencies (or wavelengths) of light are absorbed and how much

6. Transmission and Absorbance
Cuvette = type of test tube which holds the solution being analyzed
Transmittance: measure of how much light of the measured wavelength came through the solution
Absorbance: measure of how much light of the measured wavelength did not pass through the solution (was absorbed)
Measured in nanometers (nm)
= 10-9 meters
= meters
How much solar energy is absorbed by this window?

7. Absorption Spectrum Shows spectrum of light absorbed by the sample.
Objects appear the color they transmit (not absorb)
Leaf Absorption Spectrum
Absorbance

8. Absorption Spectrum of _________________
Wavelength (nm)

9. Absorption Spectrum of _________________
Wavelength (nm)

10. Absorption Spectrum of _________________
Wavelength (nm)

11. Absorption Spectrum of Sandy’s Orange Juice
Wavelength (nm)

12. Absorption Spectrum of Orange Juice Found at Crime Scene
Wavelength (nm)

13. Absorption Spectrum of Joy’s Orange Juice
Wavelength (nm)

14. Absorption Spectrum of Paul’s Orange Juice
Wavelength (nm)

15. Absorption Spectrum of Belinda’s Orange Juice
Wavelength (nm)