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Questions and Answers
What scientific field deals with the interactions of various types of radiation with matter?
Spectroscopy
What does spectrometry measure?
Intensity of radiation
Which of the following laws relates to the absorption spectrum?
The superposition principle states that the resulting disturbance from overlapping waves is the equal to the individual disturbances.
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What is refraction in the context of electromagnetic radiation?
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Which term describes the bending and spreading of waves around an obstacle?
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What is quantum yield in fluorescence spectroscopy?
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EMR as a ______ refers to the concept of electromagnetic radiation behaving as particles.
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Study Notes
Spectroscopy/Spectrophotometry
- Spectroscopy is the field of studying interactions of various types of radiation with matter
- Spectrometry is the measurement of the intensity of radiation with a photoelectric transducer or another electronic device.
Electromagnetic Radiation
- Electromagnetic radiation (EMR) can behave as both a wave and a particle
- EMR as a wave:
- Superposition: When two or more waves overlap, the resulting disturbance is the algebraic sum of the individual disturbances
- Diffraction: When waves bend and spread around an obstacle
- Transmission: When EMR passes through a medium
- Refraction: When light changes direction as it passes from one medium to another
- Reflection: When incoming light bounces off of an object
- Scattering: When light bounces off an object in various directions, dependent on wavelength and the object's size and structure
- Polarization: The direction and magnitude of the wave's electrical field
UV-Visible Spectrophotometry
- A molecular absorption method of spectrophotometry
- Measures the amount of UV or visible light absorbed by a sample
- Used to identify and quantify the presence of chemicals in a solution
Absorption Spectrum
- The visual display of the light absorbed by a sample at different wavelengths
- Shows the relationship between the wavelength of light and the amount of light absorbed
- Can be used to identify and quantify the components of the sample
Beer-Lambert Law
- Relates the absorbance of a solution to the concentration of the analyte and the path length of the light beam passing through the solution.
- Used to calculate the concentration of a substance in solution by measuring the amount of light that is absorbed by the solution.
- Formula: Absorbance (A) = εbc
- ε: Molar absorptivity, a constant that depends on the substance and the wavelength of light
- b: Path length, the distance that the light beam travels through the solution
- c: Concentration of the analyte in solution
Absorption Shifts
- Hypsochromic Shift: A shift in the absorption spectrum towards shorter wavelengths, caused by factors like the presence of electron-withdrawing groups or increased conjugation
- Bathochromic Shift: A shift in the absorption spectrum towards longer wavelengths, caused by factors like the presence of electron-donating groups or increased conjugation
IR Spectrophotometry
- A method for analyzing molecular structure
- Measures the absorption of infrared radiation by a sample
- The patterns of absorption bands in the spectrum provide information about the functional groups and structural features of the molecule.
Molecular Emission Spectrophotometry
- Methods that measure the amount of light emitted by a substance
- Used to identify substances
- Provides information on the structure and electronic properties of the substance
Fluorescence Spectroscopy
- A molecular emission method that measures the fluorescence of a sample, the amount of light emitted when a substance absorbs UV or visible light and then re-emits it at a longer wavelength.
- Variables that affect fluorescence and phosphorescence:
- Quantum yield
- Transition types
- Molecular structure
- Structural rigidity
- Temperature
- Solvent
- pH
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Description
Test your knowledge on the principles of spectroscopy and the behaviors of electromagnetic radiation. This quiz covers key concepts such as wave interactions, refraction, and the mechanisms of spectrometry. Perfect for students studying advanced physics or chemistry.
