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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

Inaugural lecture: Prof André Pelser
2004-06-04

Tendencies and changes in the South African population structure in future decades.

Within the next five years South Africa will for the first time in the past century enter a period where the death rate will exceed the birth rate, largely due to the impact of HIV / AIDS.

According to sociologist Prof André Pelser, sociologist at the of the University of the Free State’s (UFS) Department of Sociology, the death rate exceeding the birthrate is only one of three demographic trends which will fundamentally change South Africa’s population structure in the following decades.

He was speaking at the UFS in Bloemfontein during his inaugural lecture as professor this week.

Prof Pelser said that according to some models the South African population will decrease within the next five decades by between 10 and 26 percent.

A second important trend which will impact on the population structure is the progressive ageing of the population.

He said the group above 65 years is the only age category in the South African population which will witness sharp increases in the next few decades.

In the next 50 years, the group younger than 15 years will reflect a decrease of 39% and those older than 65 years in South Africa will increase by approximately 110% in the next two decades.

“The systematic “greying” of the South African population will create the same economic and welfare issues as those with which governments in some more developed countries are already grappling,” said Prof Pelser.

A third trend affecting the South African population structure is the constant decrease in life expectancy.

Life expectancy at birth for the total population is projected to decrease from approximately 62 years at the beginning of the 1990’s to 43 years in 2015-2020, with sharp differences between the various population groups.

These tendencies and changes to the South African population structure have serious implications, he said.

For example, he said, the reduction in life expectancy could compromise national development objectives.

“It is estimated that more than a quarter of the economically active population will be infected with HIV by 2006,” said Prof Pelser.

The increase in the population, in age category 65, will place a financial burden on government and the economically active sector.

“Especially worrying is the fact that ever-increasing proportions of the state budget will be allocated to health and welfare services and this at the expense of other priorities like education, infrastructure, criminal justice system and trade and industry, to name but a few,” he said

“A comprehensive and integrated strategy is thus vitally important in addressing the overarching issues caused by changes in the population structure,” said Prof Pelser.

 

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