PHYS 3650L - Modern Physics Laboratory

PHYS 3650L= - Modern Physics Laboratory

Laboratory Advanced Sheet

The Emission Spectrum of Hydrogen

1. Objectives. The objectives o= f this laboratory are

a. to study the emission spectrum of hydrogen, a= nd

b. to determine Rydberg constant.

2. Theory.

a. If a lar= ge voltage is applied across a sealed tube filled with a low-pressure gas, the= gas will emit electromagnetic radiation characteristic to the individual gas at= oms. The resulting emission spectrum consists of a collection of well-defined li= nes which is unique for a particular atom. It was discovered that the lines in = the emission spectrum of hydrogen (which was intensively studied during the nineteenth century) can be grouped into series, labeled n' =3D 1, 2,= 3, etc, with the wavelength of a particular line in a series given by the following simple expression:

<= span style=3D'font-family:Arial'>(1)

where

= ; n' = =3D 1, 2, 3,.....,

= ; n =3D n' +1, n'+2, n'+3,....= , and

R<= /i> =3D 1.097 x 10⁷ m^-1 is the Rydberg constant.

b. Balmer series, a collection of lines in the visible p= ortion of the hydrogen spectrum, is given by n' =3D 2:

<= span style=3D'font-family:Arial'>(2)



3. Apparatus and experimental proce= dures.

a. Equipmen= t.

1) Spectrometer.

2) Diffraction grating.

3) Hydrogen gas tube.

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.<= /p>

4. Requirements.

a. In the laboratory.

1) Your instructor will introduce you to the equipment to be used in the exper= iment.

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 Excel^TM 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.

Para= 3. Apparatus and experimental procedures.

1) Provide = a figure of the experimental apparatus (para 3b).=

2) Provide descriptions of the capabilities of equipment used in the experiment (para 3c).

Para= 4. Data. Data tables are included at Annex A for record= ing measurements taken in the laboratory. A copy of these tables must be includ= ed with the lab report. Provide the items listed below in your report in the f= orm a Microsoft Excel^TMsprea= dsheet showing data, calculations and graphs. The spreadsheet will include:=

1) A table = with columns for line color, measured angle of diffraction to the right, angle of diffraction to the left, mean angle of refraction, calculated wavelength, inverse wavelength, number n responsible, and 1/4 -1/n².<= /span>

2) A graph = of the inverse wavelength vs. 1/4 -1/n².

3) Regressi= on line for the inverse wavelength vs. 1/4 -1/n².

4) Experime= ntal value of the Rydberg constant.

5) Calculat= ion of the percent discrepancies in the Rydberg consta= nt.

Para= 5. Results and Conclusions.

a. Results.

1) A statem= ent regarding the agreement or disagreement between the predicted and measured dependence of wavelength on n.

2) A statem= ent of the measured value for the Rydberg constant.

2) A statem= ent of the percent discrepancy between measured and accepted values of Rydberg constant.

b. Conclusions.

1) Assess t= he accuracy of your experiment.

2) Describe= the sources of error in the experiment.

Annex A
Data

1. Diffraction grating constant.

      &n= bsp;            = ;            &n= bsp;     a =3D ___________________________________m

2. Angle of diffraction.

      &n= bsp;            = ;

Line

Diffraction Angle (degrees/minutes)

Right

Left

Spectral order, m

1

2

1

2

Violet

Bluegreen

Red

Line	Diffraction Angle (degrees/minutes)
Right	Left
Spectral order, m	1	2	1	2
Violet
Bluegreen
Red