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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

Johann swims his way to Olympics
2016-05-18


Johann van Heerden from the University of the Free State has qualified for the Paralympic Games in the swimming pool, and is now waiting to hear if he will be included in the South African team. Photo: Nadya van Heerden.

In the past couple of months, Johann van Heerden has been swimming his way to the Paralympic Games, and is still preparing as if he will be going to Rio de Janeiro.

The Kovsie swimmer, who will know whether he has been included in the Paralympic team in July 2016, feels his training is progressing well. The Olympics will be held in Brazil from 7 to 18 September 2016. If all goes well, this could be the first of several Olympics for the 20-year-old second-year Education student from the University of the Free State (UFS).

Dream year for Education student

Van Heerden (cerebral palsy), whose hero is the former Paralympic superstar Natalie du Toit, has had huge successes in the run-up to the 2016 Olympics. Among others, he was named the best senior swimmer at the Nedbank National Championships for the Physically Disabled in Bloemfontein in March 2016. At the South African Senior Championships in Durban in April 2016, he qualified for the Olympics in the 100 m breast-stroke with an A-qualifying time, and in the 50 m and 100 m freestyle with B-qualifying times.

Only three male swimmers to Olympics

However, he has to wait until the announcement of the South African Paralympic team, since only three male and three female swimmers will be selected. He will not be competing in another major event before the Olympics. “My short-term goal is to compete in this year’s Games, and, in the long term, I would like to reach even greater heights at the 2020 Games,” he said. Du Toit is an inspiration to him because “she was hard-working, and she had a lot of drive”.

Other students from CUADS also excel

At the above-mentioned National Championships, Van Heerden won a total of five gold medals (200 m medley, 100 m breaststroke, 50 m freestyle, 50 m breaststroke, and 200 m breaststroke) and one silver medal (100 m freestyle). Other students from the Center for Universal Access and Disability Support at the UFS also excelled.

Dineo Mokhosoa (cerebral palsy) won three gold medals (long jump, shot-put, and discus), while the athlete Louzanne Coetzee (blind) shattered the world record in the 5 000 m, as well as the Africa record in the 1 500 m. Juanré Jenkinson (cerebral palsy) won two silver medals (discus and shot-put) while Danie Breitenbach (blind) won two gold medals (800 m and 1500 m).

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