03Post - 9/17/2011 OBJECTIVES What is the quantitative...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
9/17/2011 1 Spectrophotometry & Beer’s Law of F o o d D y e s 1 Last Update: 9/17/2011 4:23 PM How is the absorption/transmission of light measured? How is the intensity of color related to the concentration of colored solutions? What is the quantitative basis for the color of substances? OBJECTIVES What considerations go into graphing experimental data? Questions 2 Concepts, Techniques Concepts: Absorbance Absorption Absorptivity Analytical Wavelength Beer’s Law Blank Concentration Electromagnetic Spectrum Incident Intensity Spectroscopy Spectrum Transmitted Transmittance Wavelength Purpose 3 Techniques: Visible Spectroscopy Quantitative dilution Graphing Plotting /Curve fitting Apparatus: Recording Spectrophotometer Spectronic 20 Pipet/Syringe Cuvette NO ADMITTANCE TO THE LAB WITHOUT SAFETY GOGGLES Gorilla 4 For a simple, transparent, C O L O R E D material, e.g. Can plot a graph showing the percent of light of each discrete C O L O R (wavelength, λ ) transmitted by the solution Transmitted light VIOLET CLEAR SOLUTION Incident white light I t ( λ ) I i ( λ ) I t ( λ ) 100 X I i ( λ ) %T( λ ) = R O Y G B V R OYG B V Percent Transmittance 5 BACKGROUND 0 10 20 30 40 50 60 70 80 90 100 Violet Red Green Yellow Blue UV IR Wavelength (nm) 6 % Transmittance of White Light by a Violet Solution
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
9/17/2011 2 0 10 20 30 40 50 60 70 80 90 100 WAVELENGTH (nm) Violet Red Blue Green % Absorbed Yellow % Absorbed = 100% - % Transmitted 7 % Absorbed of White Light by a Violet Solution VISIBLE AND ULTRAVIOLET: Electronic structure of molecules INFRARED REGION: Vibrations of molecules What determines INTENSITY of absorption? EFFICIENCY of INTERACTION between Molecules & Electromagnetic Radiation λ = 100 nm – 800 nm 800 nm – 100 m 8 What determines the WAVELENGTHS of light that substances absorb? A SPECTROPHOTOMETER measures the RELATIVE absorption of light of DIFFERENT WAVELENGTHS by a substance DETECTOR to measure intensity of light transmitted through sample, and ELECTRONICS to translate detector output into numbers SOURCE of light, MONOCHROMATOR –an element to select particular wavelengths SAMPLE & CONTAINER 9 Which DEVICE measures this phenomenon?
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/18/2011 for the course CHE 133 taught by Professor Robertschneider during the Spring '08 term at SUNY Stony Brook.

Page1 / 5

03Post - 9/17/2011 OBJECTIVES What is the quantitative...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online