Wavelength Selection Homework Problem Set
This problem set was developed by S.E. Van Bramer for Chemistry 366 at Widener University.
Goal:
to introduce students to several common wavelength selection techniques
Objectives:
- Students will be able to identify the performance characteristics of different types of filters
- Students will be able to describe the tradeoffs involved in monochrometer design
Introduction:
Spectrometers typically use either a filter, which transmits a limited wavelength range, or a grating, which disperses light, to select a wavelength of light for an experiment.
Filter Questions:
Melles Griot is an optics company that produces a wide range of filters. They have information available at: www.mellesgriot.com under "optics"; "filters"
- Compare the transmission efficiency of a colored glass VG9 green glass filter with an 03 FIV 309 bandpass interference filter at 500, 520, and 550 nm.
- Determine what a notch filter is used for and select one that would be appropriate to use with the second harmonic of a Nd:YAG laser. A Nd:YAG laser operates at 1064 nm.
- Sketch what you expect the transmission efficiency to be for a heat absorbing filter. Compare your expectations with a KG 2 heat absorbing filter.
- Sketch what you expect the transmission efficiency to be for a long pass cutoff filter. Compare your expectations with a GG 400 filter.
Monochrometer Questions:
Monochrometers involve tradeoffs between the spectral range, spectral resolution, transmission efficiency, and design wavelength.
- Use the technical information available at the ocean optics web site: www.oceanoptics.com to design a monochrometer with 1 nm resolution and a spectral range from 400 to 800 nm.
- If you increase the number of grooves per mm, what happens to the resolution and spectral range?
- What happens to the resolution and spectral range when the slit width is reduced?
- Look at the figures and equations in your textbook to find the information you need to explain the relationship between resolution, spectral range, and slit width.
- The ocean optics spectrometers use a CCD or diode array detector. What are the advantages and disadvantages of this detector when compared with a photomultiplier tube.
Please send comments or suggestions to svanbram@science.widener.edu
Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013
© copyright 1996, S.E. Van Bramer
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Last Updated: February 12, 2007