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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

New champions crowned at first-year athletics
2017-02-03

Description:UFS first-year athletics  Tags: UFS first-year athletics  longdesc=

It was a day filled with excitement on and off the
track when the residences at the University of
the Free State competed against each other
during the first-year athletics event.
Photo: Charl Devenish

The University of the Free State’s first-year athletics is an institution. It is a day marked by colour, spirit, and hoarse voices, but in 2017 produced something different than the last couple of years.

For the first time in four years, new athletics champions were crowned in both the men’s and women’s sections when Veritas and Sonnedou walked away with the trophies at Pellies Park on the Bloemfontein Campus on 25 January 2017.

Wag-’n-Bietjie, Vishuis relinquish titles

Sonnedou, who came second in 2016, broke Wag-’n-Bietjie’s stronghold of the past six years by winning the women’s athletics trophy. Furthermore, Sonnedou won this trophy more than a decade ago – in 2004. Veritas, who won the men’s athletics trophy for the first time since 2011, also put a stop to Vishuis’s dominance. House Abraham Fischer has worn the athletics crown for the past three years.

This year, Vishuis (70 points) took second place after Veritas (76), with Armentum (61) third. Sonnedou (99 points) easily triumphed in the women’s division, while Akasia (36) and Wag-?-Bietjie (34) respectively took second and third place.

Veritas captures overall Spirit trophy

However, the event is about much more than the action on and around the athletics track. First-years also get the opportunity to show pride in their residences by shouting at the top of their lungs.

Veritas, better-known in recent years for its excellent sêr groups, asserted itself even more by being named as the overall winner of the Spirit trophy. This residence was also the winner of the men’s section. Harmony won the Spirit trophy for women’s residences, while Conlaurês was the co-ed residence with the greatest spirit.

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