Spectrometry

Name: Trey Riley

Lab Experiment #8: Spectroscopy

Date: March 30, 2016

Abstract

          The purpose of this lab and this report is to become familiarized with the chemical compositions of elements, and the practices and methods of determining elemental composition. A spectrometer was used, as well as a diffraction grating, to see the visible spectra produced by different elemental gases, as well as continuous spectra from certain light sources. Seven sources of light were observed with a spectrometer. Our goal was to determine which element made up the gas by using data recorded from observations with the spectrometer. Once the data was recorded, our data was either confirmed or denied by online sources. These sources eventually lead us to the conclusion of the six different elements present in each light source.

Introduction

            This report has three distinctive experiments. The purpose in doing the first experiment is to become familiar with a diffraction grating and a spectrometer. A ceiling light was viewed with the diffraction grating, and the spectrum observed was to be recorded. The spectrometer was then calibrated on a light source to use for the rest of the experiment. Important features of the spectrometer were to be noted, such as the wavelength scale labeled from 700 to 400 nanometers from left to right. Proper usage was demonstrated and repeated by students, and thus the rest of the experiment began.

Spectrometer used during experiment

The second experiment conducted consisted of viewing an incandescent bulb with the spectrometer. A continuous spectrum was to be observed if the spectrometer was calibrated correctly. The patterns of color were to be noted on the wavelength scale. The end of the spectrum was also to be noted on the far left and far right to indicate the wavelength limits of the sensitivity of the human eye.

           

In the third experiment, several spectra of elements were observed at different stations. The spectrometer was to be used, and specific wavelengths were to be recorded. The color of the gas, as well, was to be noted to help indicate which element is within the unlabeled gas tubes. Specific elements emit only one color of light to the human eye. This color that we see is actually all of the different colors in the elements spectrum blended together. Pictures were to be taken of our spectra that we observed, but taking the picture was much harder than expected, viewing the spectrum through the narrow slit of the spectrometer.

           

Procedures

Throughout each individual experiment, a spectrometer or diffraction grating was used. When determining composition of gases, online sources were consulted to confirm or deny or results. If an ambiguous answer was given by an online source, another was consulted until a confirmation was given that multiple students could agree upon. Pictures were not taken of the spectrum I observed due to the difficulty of the operation. Spectra of elements were found online through a spectrometer that closely resembled what I viewed.

Results and Discussion

Experiment One

            The continuous spectrum was observed from the ceiling light using the diffraction grating. The spectrometer was calibrated, and all important features were known. In the picture, the closest to the light source is violet, while the furthest is red.

Diffraction grating of ceiling light

Experiment Two

            The continuous spectrum was observed using the spectrometer. The wavelength limits of the sensitivity of the human eye were though to be 700 to 400 nanometers, but the exact quantities seemed to be 660 and 420.

Continuous spectrum observed from desk lamp

Experiment Three

            Seven stations were observed with a spectrometer. All measurements are in nanometers, (10^(-9))m.

·         

      Station 1: Continuous spectrum observed from incandescent light bulb

·         Station 2: Emission lines observed at 655, 590, 490 

Hydrogen emission spectrum

      Observed Gas: Faint Purple 

Hydrogen gas

      Conclusion: Hydrogen

·         Station 3: Multiple emission lines observed from 700-580, 540, 535, 505  

Neon emission spectrum

     Observed Gas: Bright Red Orange 

Neon gas

      Conclusion: Neon

·         Station 4: Emission lines observed at 590, 560, 510 and 430 

Krypton emission spectrum

     Observed Gas: Bright Faint Blue 

Krypton gas

      Conclusion: Krypton

·         Station 5: Emission lines observed at 700, 660, 580, 495, 485, 463, 420, 400 

Helium emission spectrum

      Observed Gas: Faint Orange 

Helium gas

      Conclusion: Helium

·         Station 6: Emission lines observed at 615, 590, 575, 545, 495, 485 

Sodium emission spectrum

     Observed Gas: Bright Orange/Yellow 

Sodium gas

      Conclusion: Sodium

·         Station 7: Emission lines observed at 575, 545, 490, 430, 400 

Xenon emission spectrum

     Observed Gas: Bright White 

Xenon gas

      Conclusion: Xenon

           

Conclusion

The objective of this lab and report was to gain a better understanding of spectrometry. This was achieved through use of a diffraction grating and spectrometer. Different spectra were observed through different methods. Incandescent bulbs produce a continuous spectrum through a diffraction grating and a spectrometer. Each separate gas tube held a different gas with different and unique spectra. Data did not directly prove one gas, but definitely implied one gas. Some source for error may have been light from other station being observed in the spectrometer causing false readings, or possibly reading some spectra of the oxygen and nitrogen gas in air. Dealing with each type of spectra helped students gain a better and more practical application of how spectrometry is used in astronomy.