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18 April 2022 | Story Leonie Bolleurs | Photo Stephen Collett
Prof Ted Kroon
Prof Ted Kroon from the Department of Physics recently delivered his inaugural lecture on the topic What’s the use of a rainbow on the UFS Bloemfontein Campus.

“A rainbow is a natural phenomenon, the result of the refraction and reflection of the sun’s rays in drops of rain. As far as mankind is concerned, it’s a perfectly useless object and won’t make anyone money. Yet the poet who said, My heart leaps up when I behold a rainbow in the sky, only put into word the feeling of wonder and excitement we all have when we see a rainbow.”

“Every day I see a rainbow in my work; I do not need to wait to see one in the sky,” says Prof Ted Kroon, Professor in the Department of Physics at the University of the Free State (UFS), who used this phenomenon to introduce the topic of his inaugural lecture: What’s the use of a rainbow. 

“Far from being only a colourful spectacle with no practical value, rainbows are useful – and lead to useful things,” he believes. 

According to Prof Kroon, one can find examples of real rainbows and rainbow analogies used not only in everyday life, but also in physics. “Besides it being familiar devices in literature, culture, and even marketing, studies of rainbows can yield practical engineering information and may even help us to find new habitable planets,” he says.

Inspired by the many uses of a rainbow

In his lecture, he discussed the basic features of natural rainbows and how they come about. He also explored how the rainbow gives meaning to colour, and how this relates to the temperature of objects. He looked at an array of instances where the rainbow is used; from depicting the life of a star to indicating that we are sick (a thermometer) or when we need to refill a gas cylinder.
Moreover, Prof Kroon pointed out that rainbows are used in computer chips, stress identification, and to transmit internet data through underwater cables of glass fibre. He also referred to how the rainbow was harnessed as an engineering tool to measure refractive index and characterise fine droplet sprays used in industry. 

He continues, “Remarkably, the science developed to understand the natural rainbow can be redirected and applied to the optical properties of metallic nanoparticles, allowing the development of nanotechnology. Knowing how the natural rainbow works and its limitations, better systems have been developed to produce rainbows. Such rainbows have been used to discover new elements and to determine the age of the universe.”

As a member of an international community of phosphor researchers who are privileged to work with rainbows every day, he has used them to study the light-emitting properties of materials doped with bismuth. With this project – an initiative with the African Laser Centre taking place between 2016 and 2021 – he collaborated with the University of Khartoum in Sudan and trained a number of its postgraduate students. “My role included the guidance of students and the measurement and interpretation of the light-emitting properties of the materials. Our research during this time, considering more than a dozen materials, was summarised in 34 scientific publications that contributed to a greater understanding of bismuth ions as light-emitting materials,” he explains. 

Developing new materials, efficient in emitting blue light

He has been developing luminescent materials since 2006, primarily for general lighting (fluorescent tubes and LEDs) and displays (television, computer, and cellphone screens), as well as niche applications in medical and forensic science. 

As part of his current research, he is examining the effect of plasmonic metal nanoparticles on phosphor light emission. He is also exploring materials that absorb infrared light but emit visible light. “For this, I would like to consider the long-term stability of such materials and develop new materials that are more efficient in emitting particularly blue light,” he says. 

Prof Kroon holds a C2 rating from the National Research Foundation and has published more than 150 articles and book chapters, obtaining a Scopus h-index of 26.

News Archive

Teachers should deal with diversity in education - Prof. Francis
2010-10-08

At the occasion were, from the left: Prof. Jonathan Jansen, Rector and Vice-Chancellor of the University of the Free State (UFS); Prof. Francis; and Prof. Driekie Hay, Vice-Rector: Teaching and Learning at the UFS.
Photo: Jaco van der Merwe

Prof. Dennis Francis, the Dean of the Faculty of Education at the University of the Free State (UFS), recently delivered his inaugural lecture on Troubling Diversity in South African Education on the Main Campus in Bloemfontein.

He urged teachers to be open to what “diversity” might mean in a particular context and how diversity relates to either inclusion or exclusion.

“An approach that promotes the inclusion of all must be based on an understanding of how exclusion operates in ways that may have typical patterns of oppression, but differ in the specific ways that exclusion is expressed and becomes normalised in that context,” he said.

“The good teacher thus seeks to understand how these forms of exclusion may develop in the school’s context and respond through taking thoughtful action to challenge them. It may require creating a climate that enables the silent to speak and recognising that not all groups communicate in exactly the same ways.”

He said teachers also had to affirm the experiential base of learners and students. He said there was an assumption that students would be more effective practitioners if their own experience were validated and explored.

“It is crucial that the students’ own history is treated as valuable and is a critical part of the data that are reflected,” he said. “Equally important is that such stories and similar activities are intentionally processed to enable students to make the connections between personal experience and relevant theory.”

He also urged them to challenge the ways in which knowledge had been framed through oppression.

“Schools are often characterised by messages that draw on one or another form of oppression. Thus, expectations are subtly or in some cases unsubtly communicated, e.g. that girls are not good at physics, or that, while white learners are strong in abstract thought, African learners have untapped creativity, and so on,” he continued.

“For someone to integrate into their role as educators a commitment against oppression means confronting obstacles that one may previously have shied away from, such as challenging authority, naming privilege, emphasising the power relations that exist between social groups, listening to people one has previously ignored, and risking being seen as deviant, troublesome or unpopular.”

Furthermore, Prof. Francis said dealing with diversity in education was always affectively loaded for both students and teachers. He said in South Africa one injunction from educators was to be “sensitive” and thus avoid risking engagement with the contentious issues around imbalances of power.

“If both students and teachers are to confront issues of oppression and power in any meaningful way, we need to design more purposely for the difficulties they will encounter, for example, creating a classroom environment that promotes safety and trust so that all students are able to confront and deal with prejudice and discrimination. Classroom environments will need to balance the affective and cognitive in addressing issues of diversity and social justice,” he added.

He also said that teachers should recognise the need to complement changing attitudes with attempts to change the structural aspects of oppressions.

“To prevent superficial commitments to change, it is important for students to explore barriers that prevent them from confronting oppressive attitudes and behaviours. In this way students are able to learn and see the structural aspects of oppression,” he said.

“Equally important, however, is to get students to examine the benefits associated with challenging oppression. A fair amount of time must therefore be spent on developing strategies with students which they will be able to use practically in challenging oppression.”

He also advised educators to affirm the capacity of staff and learners to act and learn in ways that do not replicate patterns of oppression.

“Many South African schools have survived both the harsh repression of apartheid and the continuing legacy of oppression of various kinds. Despite that, we are often as educators made aware of the ways in which young people in particular affirm themselves and each other in creative and confident ways,” he concluded.

Media Release
Issued by: Lacea Loader
Director: Strategic Communication (acg)
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: loaderl@ufs.ac.za  
7 October 2010
 

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