Which statement about luminescence is FALSE? Select one: O a. Luminescence is emission of light from an excited state of a molecule. O b. At low concentration, emission intensity is proportional to analyte concentration. c. Emission comes at higher energy (shorter wavelengths) than absorption. d. Luminescence is quenched by self-absorption at high analyte concentrations. e. Luminescence is inherently more sensitive than absorption.

Which statement about luminescence is FALSE? Select one: O a. Luminescence is emission of light from an excited state of a molecule. O b. At low concentration, emission intensity is proportional to analyte concentration. c. Emission comes at higher energy (shorter wavelengths) than absorption. d. Luminescence is quenched by self-absorption at high analyte concentrations. e. Luminescence is inherently more sensitive than absorption.

Living by Chemistry

2nd Edition

ISBN:9781464142314

Author:Angelica M. Stacy

Publisher:Angelica M. Stacy

ChapterU5: Fire: Energy , Thermodynamics, And Oxidation-reduction

Section: Chapter Questions

Problem 19STP

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Would the light from fireflies be considered an example of a fluorescence or a phosphorescence process?
True or false? A. Phosphorescence occurs at higher energy then fluorescence. B. Fluorescence occurs at longer wavelengths than phosphorescence. C. Fluorescence occurs at shorter wavenumbers than phosphorescence.
a. When the light source is monochromatic, Beer's Law holds true. b. Beer's Law establishes a relationship between the concentration of a sample and its absorbance, wherein absorbance is the ratio of light leaving the sample to light entering it. c. For solutions that have more than one absorbing species, Beer's Law holds true even if the analytes of interest don't interact.
Which is TRUE for spectroscopy of a mixture? A. The absorbance for a mixture at a particular wavelength is the sum of the absorbances for the components that absorb at the particular wavelength. B. Spectrophotometers can differentiate between mixture components that absorb at the same wavelength. C. Each component in a mixture has the same molar absorptivity at the same wavelength. D. The concentration for each component in a mixture is easily calculated by least squares for guesses of each component when the individual spectra are well resolved.
Which of the following are true regarding phosphorescence and fluorescence? Read through all before making your one selection. A. Phosphorescence occurs at a lower frequencies than fluorescence B. Fluorescence occurs at longer wavelengths than phosphorescence. C. Fluorescence occurs at shorter wavenumbers than phosphorescence. D. B and A E. A and C F. All the above are true G. None of the above are true
A Substance that is responsible for UV-vis absorption is? A. Chromophores B. Overtones C. Photons D. Beer-lambert
4. A cuvette containing a colored solution in the path of a laser beam absorbs 12% of the incident light. If a second identical cuvette of the same solution is added to the beam path, what percentage of the incident light will reach the detector? A. More than 24% B. Less that 24% C. 24%
Which of the following explains why a more concentrated dye solution has a higher absorbance? A. There are more dye molecules in the solution so more isotopes reach the detector. b. There are more isotopes in solution to emit photons. c. There are more dye molecules in solution to emit isotopes. d. There are more isotopes in solution to emit protons. e. There are more dye molecules in the solution to absorb photons.
7. Light bouncing off the bright concrete on a sunny day a.) Reflection b.) Refraction c.) Absorption
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A protein’s concentration can be determined spectrophotometrically by mixing it with an indicator called a Bradford reagent and measuring the amount of light absorbed by the protein. Use the plot below to determine the mass of protein (in micrograms, μμg ) in 100.0 mL of the solution if its absorbance is 0.398. A. 52 B. 3.1 C. 2.4 D. 0.52 E. 0.031
Question 37 Which is TRUE for spectroscopy of a mixture? O A. The absorbance for a mixture at a particular wavelength is the sum of the absorbances for the components that absorb at the particular wavelength. B. Spectrophotometers can differentiate between mixture components that absorb at the same wavelength. O . Each component in a mixture has the same molar absorptivity at the same wavelength. O D. The concentration for each component in a mixture is easily calculated by least squares for guesses of each component when the individual spectra are well resolved.