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TED Talks about rainbows

18 April 2022 | Story Leonie Bolleurs | Photo Stephen Collett

“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 acknowledge 53 for long service

2004-11-03

Long service awards for 35 years: Mrs. Christa du Plessis, Centre for Higher Education studies and Development, mnr. John Moorosi, Soil- and Crop- and Climate Sciences , prof. Frederick Fourie, rector, prof. Jopie Botha, Institute for Groundwater Studies, me. Susan Reineke, Plant Sciences, Dr. Sarie van Vuuren of Sociology and me. Aletta de Klerk, Kovsie Sport.

Fifty three personnel members received long service awards in the centenary year of the university for respectively 35 years of service and 25 years of service.

Prof. Frederick Fourie, Rector, said to the recipients of the long service awards: “In a year in which the writing of history of the UFS took a prominent place in the Centenary celebrations and in which one relived the past hundred years, the value we add to the university on a daily basis is clearly visible. Many personnel members contributed to make the UFS a valued institution and will proceed to do that in the spirit of 100+.”

He thanked and acknowledged personnel for the plus they add to each day’s work. “The students which enter the UFS each year, want to thank you for an university which on an innovative manner impacted their lives. “You helped to create the building blocks for their future,” he said.

Prof. J. F. Botha, Mr M.G. Botha, Ms A. De Klerk, Mr M.J. Doman, Prof. H.C. Janse van Rensburg and Ms S.M.C. Reinecke received awards for 35 years of service.

For 25 years of service at the university Prof. S.L. Barnard, Mr B. Botma, Dr H. J. Breytenbach, Dr M.W. Brussow, Mr N.L. Combrink, Ms A.J. Du Plessis, Ms C. Du Plessis, Prof. L. Goedhals, Mr M.E. Hlazo, Prof. B.B. Hoek, Dr S.J.E. Janse van Vuuren, Mr M. Kgasane, Ms A. Kgosi, Dr W.P. Konig, Dr P.A.L. Le Roux, Prof. N.J. Luwes, Dr N. Luyt, Ms S.E. November, Ms M. Mabaso, Ms M.K. Maruping, Prof. J.D. Marx, Mr J.P. Masedi, Mr G. Mokapane, Mr J. Mokapane, Ms M.L. Molosi, Ms M.M. Molwagale, Mr P.J. Moorosi, Ms C. Moroagae, Ms E. Moroale, Mr G.G. Mothokwane, Prof. M. Mulder, Prof. A.C. Otto, Ms H. Pelser, Ms E. Pelzer, Ms M.M. Pheko, Prof. E. Pretorius, Ms M.P. Richter, Ms E. Rouls, Prof. M.T. Seaman, Prof. R.B. Snowdowne, Prof. J.P. Strauss, Ms M.S. Tsolo, Prof. H.J. van der Linde, Dr S. van Vuuren, Prof. J.B. van Wyk, Dr J.M. van Zyl, Prof. T. Verschoor and Ms M.H.S. York received an long service award.

“Be assured of my appreciation for your loyalty and commitment to a university which is taking careful steps into a new century of its existence. If we do the right things right and with a sincere belief in our heavenly Father we will be able to build on the solid foundation laid by people like you,” he said.

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