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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

Two UFS architecture students won prestigious PG Bison 1.618 Competition
2017-10-26

 Description: Bison read more Tags: : Stephan Diedericks, Department of Architecture, Margaux Loubser, Kobus du Preez, Zack Wessels, PG Bison 1.168 Competition 

At the PG Bison 1.618 competition awards ceremony
in Rosebank, were from the left:
Camrin Plaatjes from the University of KwaZulu-Natal;
Stephan Diedericks, winner of the competition;
and Margaux Loubser,
the second-place winner. Both Stephan and
Margaux are studying Architecture at the UFS.
Photo: Supplied



Food that reaches its sell-by date in supermarkets is usually disposed of, but has not yet reached its best-before date.  What happens to this food?  According to Stephan Diedericks, the answer to this is for this food to be repurposed.

Not only does Stephan want to prevent the waste of food – in a world where food security is a challenge – but he also won the prestigious PG Bison 1.618 Competition with his entry in which he suggests that gourmet meals be prepared from food that has reached its sell-by date, and then be served in the Delta Recycletorium. 

Students introduced to park lands in urban areas
Diedericks is a student in the Department of Architecture at the University of the Free State (UFS). Second-place winner in this competition was Margaux Loubser, also a UFS student. Another UFS student, Dehan Kassimatis, was a finalist. They received their awards at a ceremony in Rosebank, Johannesburg, earlier this month. 

The competition, now in its 24th year, was created to recognise the future interior and industrial designers, architects, and key decision-makers in the South African construction industry. It is known not only for the prestige it offers its winners, but also for the tradition-defying brief given to the students each year.

According to lecturers Kobus du Preez and Zak Wessels, in the Department of Architecture, the competition introduced the students to parklands in urban areas. He quotes the competition brief: “Rural to urban migration with the development of commercial and residential property elevates the importance of parklands within cities, in creating a refuge from the hustle of daily life.  These areas are leveraged to encourage healthier living, community interaction and environmental awareness.”

Learning experience more important than prizes
The site that was the focus of the competition is the Environmental Centre, Delta Park Heritage Precinct in Johannesburg. Students needed to transform this old building into a vibrant gastronomic restaurant. “The theme and style of the restaurant was for the student to choose,” said Du Preez. 

Loubser called her restaurant Rooted – a wholefood restaurant.  She was influenced by the geometries of the original Art Deco building. Rooted articulates and integrates the space between nature and the building.  Similar to an Art Deco painting or poster, the landscape is abstracted into terraces which are used to grow vegetables organically.  Vertical green screens soften the divide between the building and its surroundings and it provides shade.

“Our students took their clues from the existing environment and integrated it with a single idea, an abstract concept, which impressed the judges,” Du Preez said. 

Although this is a competition that is well reported in the industry press, Du Preez and Wessels agree that the learning experience for students is much more important than winning the contest. The competition’s brief aligned well with the Department of Architecture’s learning content with its urban focus.

Jacques Steyn, a UFS architecture student, came third in the competition in 2015.

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