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TED Talks about rainbows

18 April 2022 | Story Leonie Bolleurs | Photo Stephen Collett

“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

Dr Oprah Winfrey praises our university

2011-08-24

Dr Oprah Winfrey after receiving her honorary doctorate degree.
Photo: Rian Horn

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Transcription (pdf document)

“I came 8 000 miles to say, thank you, Vrystaat!” and “God bless South Africa,” were the words Dr Oprah Winfrey used yesterday to respectively open and close her address to an overflowing Callie Human Centre on our Bloemfontein Campus.

Our university awarded an honorary doctorate in Education to Dr Winfrey during a stately, yet warm and cheerful affair yesterday, which saw the 4 500 seater Callie Human Centre packed to the rafters with adoring fans, staff members and students.

The honorary doctorate is in recognition of her unparalleled dedication to improving the lives and futures of so many by improving education and ensuring that it is accessible to all. Through her award-winning show, The Oprah Winfrey Show (which concluded this year after 25 years of entertainment and service), and the various charity organisations she has established, Dr Winfrey has harnessed the power of her iconic stature in the struggle to eradicate poverty and make education accessible to all.

The ceremony’s audience was entertained by South African music legend, Ms Sibongile Khumalo, the Bloemfontein Children’s Choir, Bartimea School for the Deaf and Blind’s Sign Language Choir, and several other musical performers as well as dancers.

Dr Winfrey could not hold back her tears when Mr John Samuel, interim Director of our International Institute for Studies in Race, Reconciliation and Social Justice, described her as an “honorary daughter of South Africa”. She proved just how much the country means to her when she joined in the singing of the South African national anthem, Nkosi Sikeleli, despite struggling with the words in some parts.

According to Dr Winfrey, her interest in our university began after she had read an article by Prof. Jonathan Jansen, Vice-Chancellor and Rector, in which he emphasised the need for South Africans to stop accepting mediocrity, if ever the country is to develop to its full potential.

She asked Mr Samuel to convey her message of support to Prof. Jansen and the wheels, which led to today’s great event, were set in motion.

She also expressed her admiration of the transformation process at our university and our commitment to “reconciliation, peace and harmony”. “What has happened at the University of the Free State is nothing short of a miracle and this is truly what the New South Africa is about,” she said to loud cheers from the audience.

To emphasise her point, she called the five workers from the Reitz video to the stage and used their forgiveness and acceptance of the students responsible for the video as an example of the healing achieved at the UFS.

“Having seen this forgiveness has allowed me to expand my vision of what we can be.” She also delivered a message of encouragement and reminded students that anyone, despite their circumstances and background, could become successful and grow to overcome their obstacles, as she had done.

“Anyone can be successful if they put their mind to it, work hard and are diligent,” she said. “We must all strive for more than success, though, and fulfil the highest expression of ourselves as humans by realising who you are and what you are meant to be.”

Following her address, Dr Winfrey answered several questions from our students, giving them advice on, among other things, how to choose a career that is right for them, and good characteristics to look for in leaders and peers.

She also mentioned that several learners from the Oprah Winfrey Leadership Academy, which has its very first group of Grade 12 learners this year, would be visiting our university next month in order to help them select a university to attend next year.

Media Release
25 June 2011
Issued by: Lacea Loader
Director: Strategic Communication
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: news@ufs.ac.za

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