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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

Kesa, UFS cross-country teams shine at USSA
2016-10-24

Description: ’Manapo UFS cross-country    Tags: UFS cross-country

The Kovsies 8 km women’s team
was crowned as champions at
the USSA cross-country meeting
in Richards Bay. From the left are
Marne Mentz, Lizandre Mulder,
and Kesa Molotsane.
Photo: Sarina Cronje

The University of the Free State (UFS) not only boasts a South African women’s cross-country champion, one of its women’s teams is also the best university team in the country.
The Kovsies 8 km women’s team was crowned the winners at the University Sports SA cross-country event in Richards Bay, while the 10 km men’s team finished second.

Kovsies men take second place

The women’s team consisted of Kesa Molotsane, Marne Mentz, and Lizandre Mulder. They respectively came in first, third and fifth at the USSA meeting held at the University of Zululand on 30 September and 1 October 2016. In the women’s competition, the times of the first three competitors are used to determine the team placements.

The UFS 4 km women’s team finished in 5th place.

The successful UFS 10 km men’s team consisted of four members from the Qwaqwa Campus – Lesedi Radebe (4th), Lebohang Miya (8th), Moorosi Semase (10th), and Lindobuhle Miya (11th). In the men’s competition, the times of the first four men in each team are taken into account.

The Kovsies 4 km men’s team finished sixth.

Molotsane’s dream year continues

Molotsane, assistant officer at KovsieSport, is experiencing a dream year. On 10 September 2016 she was crowned as national cross-country champion over 10 km when she represented the Free State in George. Mentz was third in George over 4 km.

Molotsane improved her own record in the 3 000 m at the Clover athletics meeting in Bloemfontein on 15 October 2016. Her time of 09:51.03 was much better than her previous record time of 10:03.97.

In the USSA road relay in Richards Bay on 1 October 2016, the Kovsies women’s team finished third in the 3 x 2 km relay. The men came fifth in the 4 x 4 km relay.

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