Lab 1: Solar spectroscopy
By observing the light from the Sun, one can measure the Solar surface temperature, the properties of the ozone layer around the Earth, study the abundance of elements in the solar as well as the Earth's atmosphere.
By studying the solar spectrum we observe absorption dips due to various molecules and atoms in both the Solar atmosphere and in the Earth´s atmosphere. The functional form of the spectrum also gives information about the surface temperature of the Sun.
Task 1
Obtain the temperature of the solar surface by using Planck´s and Wien´s laws. The relevant theory with applicable formulas can be found in the lab manual. Wien's law gives a simple formula for calculating the temperature of a "Black body" radiator, such as the Sun -- need only to measure the wavelength of the peak of the Black body curve!
In the figure above we see the Planck curve for two temperatures, with the wavelength of the intensity peak lambda_max shifting down with increasing T.
Task 2
Find the atoms in the solar atmosphere from the so called Fraunhofer lines. A general description about how solar scientists record solar spectra, solar temperatures, and absorption of species in the Earth`s atmosphere can be found in solar recordings. The figure below shows two recordings where specific absorption lines can be identified.
By using a spectrometer with a CCD camera (see below) directed towards the Sun, either strictly at noon or at different times of the day one can measure the solar spectrum close to the surface, where much of the absorption of atmospheric molecules and atoms occur.
Task 3
The figures here illustrate measurements with amplifications 0.1X, 3X, and 10X. Click to enlarge and select the amplification you think is the optimal.
Task 4
Determine the thickness of the ozone layer. Study the lab manual, which it describes in detail how a solar spectrum can be used to perform this. See also the Lab 1 Tasks below.
Detailed spectra covering the bands of ozone recorded at different times of day are found in the list below. If you are born on dates 4th, 14th, or 24th, use line 4 (and so forth). The list format is "Day: k x 10^-4" (click to display spectrum).
0: 0.032
1: 0.40
2: 0.62
3: 0.68
4: 0.74
5: 0.80
6: 0.93
7: 1.01
8: 0.14
9: 0.18
An overview of recordings using solar spectrometers can be found here: solar recordings. One obtains the following spectral curves (see below), which depend on whether we record directly upwards or at different angles. (Measured above our atmosphere the spectra look quite different.)
A recording of the solar spectrum between 300 nm and 1.1 micrometer in Stockholm is shown above: spectrum-1. It is given as two columns, wavelength and intensity, to be imported and analyzed in Excel, Matlab or Origin.
The figure above is found in the more complete Excel file, solar recordings, where all curves are explained. However, spectrum-1 has a higher resolution.
Task summary
A complete description of the tasks of this lab is found here: Lab 1 Tasks.
Report
The report should be 2-3 A4 pages long. It should contain:
- Title: name of lab exercise, author, and e-mail address.
- Aim: the purpose of the investigation and which parts it consists of.
- Experiment: short description of the measurement. Table of measured values.
- Results: the result for the different parts of the experiment and analysis, calculations of the relevant values, preferably with uncertainties stated.
- Conclusions.