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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

Twenty years of the constitution of South Africa – cause for celebration and reflection
2016-05-11

Description: Judge Azar Cachalia Tags: Judge Azar Cachalia

Judge Azar Cachalia

The University of the Free State’s Centre for Human Rights and the Faculty of Law held the celebration of the twentieth anniversary of the adoption of the South African Constitution on 11 May 2016 on the Bloemfontein Campus.  Students and faculty members celebrated and reflected on not only the achievements of the constitution but also on perspectives regarding its relevance in modern society, and to what extent it has upheld the human rights of all citizens of South Africa.

The panel discussion started with a presentation on the pre-1996 perspective by Judge Azar Cachalia of the Supreme Court of Appeal.  Judge Cachalia reflected on his role in the realisation and upholding of the constitution, from his days as a student activist, then as an attorney representing detainees during political turmoil, and currently as a judge: “My role as an attorney was to defend people arrested for public violence. My role as a judge today is to uphold the constitution.”  He stressed the importance of the constitution today, and the responsibility institutions such as the police service have in upholding human rights.  Judge Cachalia played a significant role in drafting the new Police Act around 1990, an Act which was to ensure that the offences perpetrated by the police during apartheid did not continue in the current democratic era. Further, he pointed out that societal turmoil has the potential to make society forget about the hard work that was put into structures upholding human rights. “Constitutions are drafted in moments of calm.  It is a living document, and we hope it is not torn up when we go through social conflict, such as we are experiencing at present.”

Thobeka Dywili, a Law student at the UFS, presented her views from the new generation’s perspective.  She relayed her experience as a student teaching human rights at schools in disadvantaged communities. She realised that, although the youth are quite aware of their basic human rights, after so many years of democracy, “women and children are still seen as previously disadvantaged when they should be equal”. She pointed out that, with the changing times, the constitution needs to be looked at with a new set of eyes, suggesting more robust youth engagement on topics that affect them, using technology to facilitate discussions. She said with the help of social media, it is possible for a simple discussion to become a revolution; #feesmustfall was a case in point.

Critical perspectives on the constitution were presented by Tsepo Madlingozi of University of Pretoria and University of London. In his view, the constitution has not affected policy to the extent that it should, with great disparities in our society and glaring issues, such as lack of housing for the majority of the poor.  “Celebration of the constitution should be muted, as the constitution is based on a decolonisation approach, and does not directly address the needs of the poor. The Constitutional Court is not pro-poor.”  He posed the question of whether twenty years on, the present government has crafted a new society successfully.  “We have moved from apartheid to neo-apartheid, as black elites assimilate into the white world, and the two worlds that exist have not been able to stand together as a reflection of what the constitution stands for.”

Prof Caroline Nicholson, Dean of the Faculty of Law, encouraged more open discussions, saying such dialogues are exactly what was intended by the Centre for Human Rights. She emphasised the importance of exchanging ideas, of allowing people to speak freely, and of sharing perspectives on important issues such as the constitution and human rights.

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