Physics307L:People/Gibson/Notebook/071105
Balmer Series
Objectives
In this experiment we will observe the Balmer Series of Hydrogen and Deuterium.
- Review basic atomic physics.
- Calibrate an optical spectrometer using the known mercury spectrum.
- Study the Balmer Series in the hydrogen spectrum.
- Determine the Rydberg constant for hydrogen.
- Compare hydrogen with deuterium
Set Up
We first plugged the mercury tube into the lamp and let it warm up for at least 5 minutes. After this we checked to see if the following values of lambda would result in giving the correct color spectra of mercury i.e. this:
- 404.7 nm (deep violet very hard to see!!)
- 435.8 nm violet
- skip (very weak blue-green)
- 546.1 nm green
- 577.0 nm yellow
- 579.0 nm yellow
- 690.75 nm red
And this is the calibration step. The values of lambda (in nm) are reached by rotation of a knob with specific values of lambda on it.
Our values of lambda for the mercury are:
Violet: 436.4 nm Green: 548.1 nm Yellow 1: 580.2 nm Yellow 2: 582.1 nm Red: Cannot see
Data
- Hydrogen
Color | Violet 1 nm | Violet 2 nm | Blue nm | Red nm |
---|---|---|---|---|
Quantum Number | [math]n=6[/math] | [math]n=5[/math] | [math]n=4[/math] | [math]n=3[/math] |
Measurement | ||||
1 | 410.5 | 432.9 | 486.5 | 660.9 |
2 | 410.0 | 433.2 | 486.9 | 661.1 |
3 | 409.5 | 433.6 | 487.2 | 660.9 |
4 | 410.5 | 433.5 | 487.8 | 660.7 |
5 | 410.5 | 433.6 | 486.5 | 660.5 |
6 | 410.25 | 433.2 | 486.5 | 660.5 |
7 | 410.0 | 433.6 | 486.5 | 660.7 |
- Deuterium
Color | Violet 1 nm | Violet 2 nm | Blue nm | Red nm |
---|---|---|---|---|
Quantum Number | [math]n=6[/math] | [math]n=5[/math] | [math]n=4[/math] | [math]n=3[/math] |
Measurement | ||||
1 | 410.0 | 432.1 | 486.0 | 660.0 |
2 | 410.0 | 433.1 | 486.1 | 660.1 |
3 | 409.75 | 433.2 | 486.5 | 660.1 |
4 | 409.75 | 433.1 | 486.5 | 660.0 |
5 | 409.75 | 433.1 | 486.2 | 660.0 |
6 | 410.0 | 433.1 | 486.2 | 660.0 |
7 | 410.0 | 433.1 | 486.6 | 660.0 |
- Neon
Color | Yellow nm | Red nm |
---|---|---|
Quantum Number | [math]n=4[/math] | [math]n=3[/math] |
Measurement | ||
1 | 580.3 | 642.0 |
2 | 585.8 | 642.0 |
3 | 585.6 | 642.1 |
Analysis
[math]R=\frac{1}{\frac{\lambda}{4}-\frac{\lambda}{n^2}}[/math]
- Using excell to find the mean wavelength for each color of Hydrogen and Deuterium, we find:
Color | Violet 1 nm | Violet 2 nm | Yellow nm | Red nm |
---|---|---|---|---|
Quantum Number | [math]n=6[/math] | [math]n=5[/math] | [math]n=4[/math] | [math]n=3[/math] |
Hydrogen | ||||
Mean | 410.1786 | 433.3714 | 486.8429 | 660.7571 |
STD Deviation | .3740 | .2752 | .5028 | .2225 |
Deuterium | ||||
Mean | 409.89 | 433.12 | 486.40 | 660.02 |
STD Deviation | .1336 | .3860 | .2309 | .0487 |
- Using the formula given above we find that the Ryberg Constant for each color of Hydrogen and Deuterium is:
Color | Violet 1 nm | Violet 2 nm | Yellow nm | Red nm |
---|---|---|---|---|
Hydrogen | ||||
Rydberg R (m^-1) | [math]1.0971\times 10^7[/math] | [math]1.0988\times 10^7[/math] | [math]1.0955\times 10^7[/math] | [math]1.0897\times 10^7[/math] |
Deuterium | ||||
Rydberg R (m^-1) | [math]1.0978\times 10^7[/math] | [math]1.0994\times 10^7[/math] | [math]1.0965\times 10^7[/math] | [math]1.0909\times 10^7[/math] |
- Now taking the mean of the measured Rydberg Constant R for each element, we find:
- For Hydrogen: [math]R_H=\left(1.0953 \pm .0039\right)\times 10^7 {m^-1}[/math]
- For Deuterium: [math]R_H=\left(1.0962\pm .0037\right)\times 10^7 {m^-1}[/math]
Results
The value we found for Hydrogen was:
- [math] R_H = 10 967 758.341 \pm 0.001\,\mathrm{m}^{-1} \ [/math]
As one can see, our value does not stray too far from the accepted value:
- For Hydrogen: [math]R_H=\left(1.0953 \pm .0039\right)\times 10^7 {m^-1}[/math]
The accepted value of the Ryderbeg constant for Deuterium is: [math]R_D=\left(1.09707 \pm .7\right)\times 10^7 {m^-1}[/math]
Again, our value was very close to the accepted value:
- For Deuterium: [math]R_D=\left(1.0953 \pm .0039\right)\times 10^7 {m^-1}[/math]
Analysis
From the way we performed our experiment, the results could not have been better. It was very difficult trying to see the lines for each, but by keeping our precision high when recording our values proved to help us in the end. Taking the data could involve some sort of error seeing as aligning the lines on the cross hairs exactly was quite eye straining.
All our values we're very close to the accepted ones we found online so it was comforting to say the least that this equipment (aged) could still give good data given the situation.