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Questions and Answers
What are the two main energy strategies used by organisms?
What are the two main energy strategies used by organisms?
Riboflavin absorbs light primarily in the blue region of the visible spectrum.
Riboflavin absorbs light primarily in the blue region of the visible spectrum.
True
What is the definition of photometry?
What is the definition of photometry?
Photometry is the measurement of light absorption by compounds.
What are the three parts of Lambert's law?
What are the three parts of Lambert's law?
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What is the statement of Beer's Law?
What is the statement of Beer's Law?
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Study Notes
Absorption and Color Perception
- White light contains all visible wavelengths
- Colored compounds absorb specific wavelengths
- Transmitted wavelengths are perceived as color
- Riboflavin absorbs primarily in blue region (max absorption at 450 nm)
- This absorption removes blue light, leaving other wavelengths (red and green) to be transmitted
- These wavelengths appear yellow
- Riboflavin also absorbs UV light (at 260nm and 370nm) but does not affect perceived color because it is outside the visible range (400-700 nm).
Photometry
- Photometry measures light absorption by compounds
- Analyzes substances qualitatively (what is present) and quantitatively (how much is present)
- Absorption spectrum extends across different electromagnetic spectrum regions
- UV region: 200-400 nm
- Visible region: 400-700 nm
- Near-infrared (IR) region: 700-900 nm
Lambert's Law
- Light absorption is independent of incident light intensity
- Proportional to the thickness of absorbing medium (solution)
- Each layer absorbs the same fraction of light that enters
- Used in determining compound concentration in solutions
Beer's Law
- Light absorption is directly proportional to the number of absorbing molecules in the light's path.
Qualitative Photometric Assays
- Analyzes absorption spectra to identify compounds
- Compounds absorb light at specific wavelengths forming unique patterns
- Comparing unknown spectra with known substances reveals compounds
Key Features
- Full-spectrum analysis provides detailed structural information
- Wavelength-specific analysis quickly identifies compounds using characteristic wavelengths (like 260/280 nm ratio for nucleic acids and proteins).
Considerations
- Conditions such as pH and ionic strength can affect absorption
- Always document solution conditions to ensure accurate comparisons.
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Description
Test your understanding of how colored compounds absorb specific wavelengths of light and how this affects color perception. This quiz covers key concepts in photometry and Lambert's law related to light absorption. Assess your knowledge on the properties of riboflavin and its effects on visible and UV light.
