Spectrophotometer Flashcards

Properties of Light

• Wave-particle duality describes how light exhibits properties of both waves and particles.
• Particle property: Light acts as a particle that conveys energy and is affected by gravity.
• Wave property: Light travels in waves; energy depends on wavelength.

Key Terms

• Wavelength: Distance of one complete wave cycle of electromagnetic radiation (EMR).
• Amplitude: Height of a wave that determines light intensity.
• Frequency: Number of waves passing a point in a given time.

Light Characteristics

• Monochromatic light: Light consisting of one color, e.g., LED.
• Polychromatic light: Light made up of multiple colors, e.g., sunlight.

Principles of Absorbance

• Selective absorbance: A solution's capacity to absorb specific wavelengths while transmitting others.
• Spectrophotometer: An instrument to measure light intensity through a sample.

Electromagnetic Spectrum

• A continuum of radiation from gamma rays to radio waves.
• Ultraviolet range: Not visible, wavelengths from 220-380 nm.
• Visible region: Wavelengths ranging from 380-700 nm.

Beer's Law

• Absorbance (A) is directly proportional to concentration (C).
• A = a * b * C, where 'a' is molar absorptivity, 'b' is the path length, and 'C' is concentration.
• Deviations occur with non-monochromatic light, extreme concentrations, and solvent absorption effects.

Spectrophotometer Components

• Light source provides EMR; common sources are incandescent tungsten lamps.
• Monochromators isolate individual light wavelengths.
• Types include glass colored filters and interference filters which allow selective wavelength passage.
• Prisms and diffraction gratings are used to separate light into its component wavelengths.

Sample Handling

• Sample cell (cuvette) holds test solutions and comes in various shapes.
• Blank: A solution without the analyte used to zero the instrument.

Detection Methods

• Photodetectors convert transmitted light to electrical energy; types include photocells and photomultiplier tubes.
• Photomultiplier tubes are more sensitive than standard phototubes, amplifying the detected signal.

Reactions and Measurements

• Kinetic reactions measure enzyme activity, useful for quantifying concentrations.
• Fixed time methods stop reactions after a set period for measurement; continuous monitoring assays take regular absorbance readings over time.

Importance of Maintenance

• Regular maintenance and function verification of the spectrophotometer are crucial for accurate results and adherence to Beer's law conditions.

Test your knowledge on the properties of light with these flashcards. The quiz covers key concepts such as wave-particle duality, particle properties, and wave properties of light. Ideal for students studying optics and related fields.