Out-of-class Questions: Instrumental Setup of a Spectrophotometer
- Page ID
- 96082
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Sources
- Describe the desirable features of a radiation source for a spectrophotometer.
- 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.
- Examining the plots above, what does this suggest about the power that exists in radiation sources for the infrared portion of the spectrum?
- Explain the advantages of a dual- versus single-beam spectrophotometer.
Lasers
- Why is it impossible to create a 2-level laser?
- 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?
- Which of the two (3- or 4-level system) is generally preferred in a laser and why?
Monochromators
- 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.
- 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
- Explain how a photomultiplier tube works. What are any advantages or disadvantages of a photomultiplier tube?
- Describe a photodiode array detector. What advantages does it offer over other detection devices?