Lab 1: Solar spectroscopy

By observing the incoming light from the Sun, wone can measure the Solar surface temperature, the properties of the ozone layer around the Earth, study the elemental abundances of the solar atmosphereelements in the solar as well as the Earth's atmosphere.

[IMAGE]

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 curvefunctional form of the spectrum also gives information about the surface temperature of the Sun.

Task 1 InvestigateObtain the temperature of the solar surface by using Planck´s and Wien´s laws. Theory and relevant theory with applicable formulaes 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. Just -- need only to measure the wavelength of the peak of the Black body curve!

[IMAGE]

In the figure above we see the Planck curve for two temperatures and how, with the wavelength ofor the intensity peak moveslambda_max shifting down with increasing T.

Task 2 Find the atoms ofin 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. Below areThe figure below showns two recordings where specific absorption of radiation can be founlines can be identified.

[IMAGE]

By using a spectrometer with a CCD camera (Ssee below) directed towards the Sun, either direstrictly at Nnoon or at different times of the day wone can measure the solar spectrum close to ground, whythe surface, where much of the absorption of atmospheric molecules and atoms occur.

[IMAGE]

Task 3 On the computer scFigures below illustrate measuremen one can click a box forts with amplification,s 0.1x, 3x and 10x. Test the boxesClick to enlarge and select the amplification you think is the bestoptimal.

http://kurslab.physics.kth.se/~berg/SolAmp0.1x.jpg http://kurslab.physics.kth.se/~berg/SolAmp3x.jpg http://kurslab.physics.kth.se/~berg/SolAmp10x.jpg

Task 4 Determine the thickness of the ozone layer. Study the lab instruction. It showmanual, which it describes in detail how thea solar spectrum can be used to perform this. See also TASKSthe Lab 1 Tasks below.

Detailed spectrum of the part covering the bands of ozone recorded at different times of day is found in the Table below. If you are born June 4 click thon dates 4th, 14th, or 24th, use Table 4, etc.

An overview of recordings using solar spectrometers can be found here: solar recordings. We getOne obtains the following spectral curves (Ssee below), which depending on ifwhether we record directly upwards or at different angles. A(Measured above our atmosphere the spectra look quite different as well.)

[IMAGE]

A recording of the solar spectrum between 300 nm and 1.1 micrometer in Stockholm with a spectrometeris 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, Sspectrum-1 has a higher resolution.

Task summary A complete description aboutof the tasks of this lab exercise is found here: Lab 1 Tasks.

Report The report should be 2-3 A4 pages long. It should contain:

* Title. N: name of lab exercise, author, and e-mail address.
* Aim. T: the purpose of the investigation and which parts it consists of.
* Experiment. S: short description of the measurement. Table of measured values.
* Results. T: the result for the different parts of the experiment and used formulas. Canalysis, calculations of measuredthe relevant values, preferably with uncertainties stated.
* Conclusions.