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Out-of-class Questions: Instrumental Setup of a Spectrophotometer

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    Sources

    1. Describe the desirable features of a radiation source for a spectrophotometer.
    2. Plot the relative intensity of light emitted from an incandescent light bulb (y-axis) as a function of wavelength (x-axis). This plot is a classic observation known as blackbody radiation. On the same graph, show the output from a radiation source that operated at a hotter temperature.
    3. Examining the plots above, what does this suggest about the power that exists in radiation sources for the infrared portion of the spectrum?
    4. Explain the advantages of a dual- versus single-beam spectrophotometer.

    Lasers

    1. Why is it impossible to create a 2-level laser?
    2. Using your understanding of a 2-level system, explain what is meant by a 3-level and 4-level system. 3- and 4-level systems can function as a laser. How is it possible to achieve a population inversion in a 3- and 4-level system?
    3. Which of the two (3- or 4-level system) is generally preferred in a laser and why?

    Monochromators

    1. Explain in general terms the mechanism in a prism and grating that leads to the attainment of monochromatic radiation. Compare the advantages and disadvantages of each type of device. What is meant by second order radiation in a grating? Describe the difference between a grating that would be useful for the infrared region of the spectrum and one that would be useful for the ultraviolet region of the spectrum.
    2. Explain the significance of the slit width of a monochromator. What is the advantage(s) of making the slit width smaller? What is the disadvantage(s) of making the slit width smaller?

    Detectors

    1. Explain how a photomultiplier tube works. What are any advantages or disadvantages of a photomultiplier tube?
    2. Describe a photodiode array detector. What advantages does it offer over other detection devices?

    This page titled Out-of-class Questions: Instrumental Setup of a Spectrophotometer is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Thomas Wenzel via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.