PHYS 3650L= - Modern Physics Laboratory
Laboratory Advanced Sheet
The Emission Spectra
1. Objectives. The objective of= this laboratory is to identify an unknown gas by studying its emission spectrum.=
2. Theory.
If a large =
voltage
is applied across a sealed tube filled with a low-pressure gas, the gas will
emit electromagnetic radiation characteristic to the individual gas atoms. =
The
resulting emission spectrum consists of a collection of well-defined lines =
which
is unique for a particular atom. By studying the emission spectrum of an
unknown gas it is possible to reliably identify it.
3. Apparatus and experimental proce= dures.
a. Equipmen= t.
1) Spectrometer.
2) Diffraction grating.
3) Several gas tubes.
b. Experime= ntal setup. To be provided by the student.
c. Capabili= ties. To be provided by the student.
d. Procedur= es. Detailed instructions are provided in paragraph 4 below.
4. Requirements.
a. In the laboratory.
1) Your instructor will introduce you to the equipment to be used in the experiment.
2) Measurements to determine the angles of diffraction will be made for three different lines in the spectrum of hydrogen.
3) Your instructor will discuss methods to be used to prepare your data for plotting using the Microsoft ExcelTM spreadsheet program.
b. After the laboratory. The items listed below = will be turned in at the beginning of the next laboratory period. A complete laboratory report is not required for this experiment.
1) Provide = a figure of the experimental apparatus (para 3b).=
2) Provide descriptions of the capabilities of equipment used in the experiment (para 3c).
1) For each= gas tube: a table with columns for line color, measured angle of diffraction to= the right, angle of diffraction to the left, mean angle of refraction, and calc= ulated wavelength.
a. Results.
1) A statem=
ent identifying
the unknown gases.
b. Conclusions.
1) Make a c= onclusion about the ability of the technique based on the emission spectra to identify the unknown gases.
2) Describe= the sources of error in the experiment.
Annex A 1. Diffraction grating constant. &n=
bsp; =
; &n=
bsp;
a =3D ___________________________________m 2. Angle of diffraction, 1st
order. =
a.
Unknown gas tube 1. &n=
bsp; =
;
Line (Color) Diffraction Angle (degrees/minutes) Right Left b. Unknown =
gas tube
2. &n=
bsp; =
;
Line (Color) Diffraction Angle (degrees/minutes) Right Left c. Unknown =
gas tube
3. &n=
bsp; =
;
Line (Color) Diffraction Angle (degrees/minutes) Right Left
Data