Download SPECTRAL WORKSHOP

SPECTRAL WORKSHOP
OVERVIEW
I
STEP-BY-STEP GUIDE

A.
Equipment List

B.
Workshop guides
II

ADDITIONAL MATERIAL
A.
Picture of the lamps, professional spectroscopes and 'DIY'
spectroscopes

B.
III
Larger view of the 'DIY' spectroscopes
HANDOUTS & WORKSHEETS

A.
Spectra of various gases

B.
Solar absorption spectra

C.
'Guess the gas' answer sheet

D.
Extra-solar Planet atmosphere absorption plot
www.sepnet.ac.uk
1
I
STEP-BY-STEP GUIDE
A.
Preparation Before Workshop
A1. FULL EQUIPMENT
CHECKLIST
Laminate showing HST
extra-solar planet spectra
Scissors (one per student or
group)
Opaque adhesive tape
•
•
•
•
•
•
•
B.
Card tube (one per student
or group)
CD (one per student or
group)
Four gas discharge tubes
and power supplies
Pocket spectrometers
Laminates showing the
spectra of different
elements and the solar
emission spectra
•
A2. OPTIONAL EQUIPMENT
•
•
•
Prism
Diffraction grating paper
Digital camera, video
capture equipment and
laptop
Workshop Guides
B1. Safety Notices
B2. Introduction to Spectra
B3. Making a 'DIY' Spectrometer
B4. Using the 'DIY' Spectrometer
B5. Applications of Spectrometers
B4.1 The Sun
B4.2 Extra-solar planets
2
Spectral Workshop
KEY
WORK TO BE DONE
TALKING POINTS
B1. SAFETY NOTICES
•
Do not look directly at the sun, with or without a spectroscope.
B2. INTRODUCTION TO SPECTRA
•
Ask if anyone knows what a spectra is, or if anyone has ever
seen one. Mention rainbows, and ask if anyone knows how they are
formed.
•
Show a spectrum using a prism.
•
Explain that spectra are like the colourful finger-prints of gases
– each gas has a unique spectral 'finger-print'. A solar spectra shows
the finger-print of all the gases in the sun.
•
Examining spectra allows us to see the chemical composition of
stars and planets from afar.
B3. MAKING A 'DIY' SPECTROMETER
•
A spectrometer is a device for splitting light into it's constituent
colours.
•
Using the diagram below as a guide, construct a spectrometer.
It is of particular importance that the slit should be 0.1 to 1mm.
www.sepnet.ac.uk
3
Tape or card
Card tube/box
Gap <1mm
Gap MUST be parallel to the CD
30O
4cm
7cm
B4. USING THE 'DIY' SPECTROMETER
•
Use the 'DIY' spectrometers to look at a light bulb, a fluorescent
tube and the sky (a safe solar spectrum).
•
Stress that science is about making observations and recording
them.
•
Set up the four gas lamps, and get the students to use their
spectrometers (or the professional ones) to guess which gas is in
each of the lamps. After 15 minutes or so, reassemble and reveal the
answers.
B5.1 THE SUN
•
The sun is a collection of many different chemicals giving off
light at many different wavelengths, so we see an almost continuous
distribution of light.
•
Explain the difference between an emission and an absorption
spectra.
4
Spectral Workshop
•
Show a solar absorption spectra, and ask if the student can
identify the element corresponding to the dark lines. These
correspond to Helium, which was first discovered on the sun (hence
the name – from the Greek 'helios').
B5.2 EXTRA-SOLAR PLANETS
•
In the last 15 years or so, telescopes have become powerful
enough to observe planets orbiting distant stars. When the planet
moves in front of the star, it hides some of the star's light – this can
be observed with a back-garden telescope as a periodic decrease in
the light from the star.
•
Professional telescopes can see what wavelengths are absorbed
by the atmospheres of these planets. Ask the students to identify the
elements corresponding to a laminate of a HST spectra. The spectra
shows light from a planet with a sodium rich atmosphere – something
very strange for us.
•
We are looking for a planet an atmosphere rich in oxygen,
nitrogen and carbon dioxide – one that can support life as Earth can.
This is how we will first detect life on a distant planet – with
spectroscopy.
www.sepnet.ac.uk
5
II
•
ADDITIONAL MATERIAL
Picture of the lamps, professional spectroscopes and 'DIY'
spectroscopes:
•
6
Larger view of the 'DIY' spectroscopes:
Spectral Workshop