Lab 1: Solar spectroscopy

By observing the incoming light from the Sun, we can measure the Solar surface temperature, the ozone layer around the Earth, study the elemental abundances of the solar atmosphere as well as the Earths 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 curve form of the spectrum also gives information about the surface temperature of the Sun.

Task 1

Investigate the temperature of the solar surface by using Planck´s and Wien´s laws. Theory and formulae 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 measure the wavelength of the peak of the Black body curve!

In the figure above we see the Planck curve for two temperatures and how the wavelength for the intensity peak moves.

Task 2

Find the atoms of the solar atmosphere, 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 are shown two recordings where absorption of radiation can be found. 

By using a spectrometer with a CCD camera (See below) directed towards the Sun, either directly at Noon or at different times of the day we can measure the solar spectrum close to ground, why absorption of atmospheric molecules and atoms occur.

Task 3

On the computer screen one can click a box for amplification, 0.1x, 3x and 10x. Test the boxes and select the amplification you think is the best.

Task 4

Determine the thickness of the ozone layer. Study the lab instruction.  It shows in detail how the spectrum can be used to perform this. See also 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 the Table 4 etc.

An overview of recordings using solar spectrometers can be found here: solar recordings. We get the following spectral curves (See below) depending on if we record directly upwards or at different angles. Above our atmosphere the spectra look quite different as well.

A recording of the solar spectrum between 300 nm and 1.1 micrometer in Stockholm with a spectrometer shown above: spectrum-1. It is given as two columns, wavelength and intensity to be imported in Excel, Matlab or Origin.

The figure above is found in the more complete Excel file, solar recordings, where all curves are explained. However, Spectrum1 has higher resolution.

Task summary

A complete description about 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. 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 used formulas. Calculations of measured values, preferably with uncertainties
• Conclusions