Faculty of Sciences
e-Science Teachers Pack
Issue 13, May 2015
Blink and you’ll miss it: Watching ultrafast photochemical reactions
Summary & learning outcomes
Light is at once both obvious and mysterious. But what exactly is it? Is it a singular beam that
appears from no-where or is it a complex combination of colours and waves which provide us with
warmth while staving off darkness? How did we even figure all this out in the first place and what
does it all have to do with solar energy? In this pack, students will learn about how spectroscopy is
helping scientists to understand the role of light in chemical reactions. They will also discover how
ultrafast spectroscopy is being used to study a range of materials - particularly those used in
polymer solar cells - at a cellular level, and how changes can be made to make them more efficient
at harnessing the power of the sun and producing solar energy.
Learning outcomes:
 Spectroscopy is the study of interactions between matter and electromagnetic radiation or light
 Light is used to create chemical reactions within particular materials, like semiconducting
polymers in solar panels, which then lead to the generation of energy
 Transient absorption spectrometers measure the wavelengths of light a material absorbs and
how it changes over time which can lead to insight into where energy loss during production
occurs
Prior learning
Students will more than likely be able to tell you where we get light from (i.e. the sun, light bulbs etc.)
They may think it is seen in only beams of light and not realise that it is actually many colours mixed
together. Determine level of understanding and cover some areas about light (including the
properties) before reading the article so that concepts are more easily understood.
 Brainstorm what students already know about light. Where do we get our light from? Do we have
natural light and artificial light? Is light a single colour or many colours mixed together? Does light
travel as a wave, a ray or a stream of particles?
Curriculum
View the relevance of this article and its resources to the Australian Curriculum:
www.sciences.adelaide.edu.au/schools-resources/docs/curriculum-issue13-blink-and-you'll-missit.pdf
Lesson plan & learning activities
Lesson 1 – Introduction to Spectroscopy
 Brainstorm what students already know about light. Where do we get our light from? Do we have
natural light and artificial light? Is light a single colour or many colours mixed together? Does light
travel as a wave, a ray or a stream of particles? Did the students know that visible light is on the
Electromagnetic spectrum? Do they know where it is placed? What are some common properties
of light? (These could include absorption, reflection, refraction and diffraction.) How do we
measure light? What instruments would be used?
 Introduce spectroscopy through reading “Blink and you’ll miss it: Watching ultrafast
photochemical reactions” (Issue 13, May 2015) article as a class (organise students into pairs or
small groups to share resources).
 Images within the article can be utilised (printed out or used on an interactive whiteboard) to
reinforce points of importance.
 Discuss with the students (as a class) what they learned from the article. Find out:
o Were there things that they already knew about spectroscopy but reluctant to mention
during brainstorming?
o What things didn’t they know? Did they learn anything interesting?
o Are there things they want to find out more about from the article?
 Define any unknown words and use them to create glossary of keywords.
 View Videos (see resources list below) if there is time (otherwise show at start of 2nd lesson).
Lesson 2 – Make your own Spectroscope
 Show videos if you didn’t have time in the first lesson.
 Quick review of points from e-Science article.
 You can see the spectra emitted by different light sources easily with your own spectroscope.
Making your own spectroscope from commonly available materials is actually pretty straight
forward. Live Science has a great tutorial using a CD to reflect the light. You can find the
instructions and list of materials on their website:
www.livescience.com/41548-spectroscopy-science-fair-project.html
 You can use your newly crafted spectroscope to look at different types of light and view their
spectra. You should be careful to never look directly at the sun using the spectroscope, but you
can look at sunlight reflected on a wall quite safely. Other sources of safe light to look at are
different types of bulbs including street lamps, neon signs and those in a flashlight, and
candlelight.
 What do you notice about the different types of light? How does this reflect the way each type of
light is made? (Hint: think about the materials that are generating the light.)
Resources
Videos (can be shown through a PC or interactive whiteboard):
 Strobe lights appear to slow everything down. See the explanation of how this works here.
http://youtu.be/OtxlQTmx1LE
 SciShow tells us all about the value of solar power, how a traditional panel works, and how some
other methods are being used to improve their efficiency.
http://youtu.be/4uPVZUTLAvA
 This video goes through one example of how understanding and altering the materials used in
solar cells can improve the efficiency of the cell. The science in this TEDx video may be a little
complex for our more junior readers.
http://youtu.be/yMaWEb4Jj5w
 Confused about light absorption and emission spectra? These videos explain how it all works.
http://youtu.be/fPt0jXHwqUw
The University of Adelaide
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http://youtu.be/1JrO7QQ1o1M
 Transient absorption spectroscopy and some of its applications are shown in this video from the
University of Auckland. There’s a bit if jargon in the beginning, but the great visuals demonstrate
the concept clearly.
http://youtu.be/RFFfYlq3oEo
Useful Websites
 The Physics classroom has a great section on spectra and how colour vision works.
www.physicsclassroom.com/class/light/Lesson-2/The-Electromagnetic-and-Visible-Spectra
 Astronomers also use absorption spectra in their work to identify what stars are made of. You can
have a go at doing this yourself using this applet.
www.learner.org/teacherslab/science/light/color/spectra/index.html
 The light-sensitive chemicals in the eye have their limits. Learn about how over sensitisation
causes a familiar phenomenon and try it for yourself using the instructions given on this website
from the Exploratorium.
www.exploratorium.edu/snacks/afterimage/index.html
Materials
 “Blink and you’ll miss it: Watching ultrafast photochemical reactions” (e-Science Issue 13, May
2015). This can be supplied on iPad or printed out from the web edition here:
www.sciences.adelaide.edu.au/schools-resources/e-science/
 Make your own Spectroscope activity:
www.sciences.adelaide.edu.au/schools-resources/docs/activity-make-your-own-spectroscope.pdf
Assessment
Teachers should choose assessment rubrics relevant to the year level and topic that they are
teaching.
Summative assessment:
 Make your own Spectroscope activity – Teachers can elect to assess how students work during
the building of spectroscopes and also have students complete an activity about the different
types of light that are seen and how each type of light is made as well as visible light and the
electromagnetic radiation spectrum
Formative assessment:
 Contributions to discussions
 Glossary of words
The University of Adelaide
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