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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

UFS Rector takes three months sabbatical leave
2008-05-05

The Rector of the University of the Free State (UFS), Prof. Frederick Fourie, has announced that he will be taking three months sabbatical leave as from Thursday, 8 May 2008.

Prof. Fourie recently made the request for sabbatical leave to the Chairperson of the UFS Council, Judge Faan Hancke. The request was approved given the fact that Prof. Fourie has occupied a number of demanding top-management posts for almost nine years, during which time he had to manage a number of major changes at the UFS.

According to Prof. Fourie, he originally wanted to go on sabbatical leave in the second half of 2007 before the start of his second term as rector, but it was not possible at that stage.

He was last on sabbatical in 1996 before he became Dean of the Faculty of Economic and Management Sciences in 1997 and Vice-Rector: Academic Operations in 1999.

He could not take his next five-yearly leave because in the post of vice-rector he was tasked with leading the financial-turnaround strategy for the UFS from the year 2000 and had to act as rector when the previous rector, Prof. Stef Coetzee, was on sick leave. Since being inaugurated as rector in 2003, there was also no opportunity to take leave as a result of the many key projects and urgent initiatives.

The Vice-Rector: Academic Operations and vice-chairperson of the Senate, Prof. Teuns Verschoor, will be the acting rector. Management processes and decision-making will continue as normal under the leadership of the acting rector together with the Executive Committee of the Executive Management (Exco) and the Executive Management. This applies to the decision about the future of the Reitz Residence as well as the continuing implementation of the policy on diversity in student residences.

According to Judge Hancke it was important that Prof. Fourie took sabbatical leave in the light of the long period he has been at the forefront of very demanding changes. There are many challenges that still lie ahead.

During his leave Prof. Fourie will be involved with the Higher Education South Africa (HESA) investigation into diversity and racism on campuses, with research and a national conference on institutional culture, as well as the Association of Commonwealth Universities (ACU) benchmarking project and its conference in Australia at the end of August 2008.

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