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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

Prof. Letticia Moja a winner in her category

2004-08-17

Prof. Moja a finalist in award
'Every member of staff is important to me'

Michelle Cahill - Bloemnuus

IF you are in need of a dose of inspiration, try and get an appointment with Prof. Letticia Moja, the Dean of the Faculty of Health Science at the University of the Free State. It will not be easy as she has an extremely tight schedule, over and above being a finalist in the 2004 Shoprite/Checkers Woman of the Year competition.

Although not a born and bred Free Stater, this dynamic woman has come to love the Free State. "Once you get past the mindset of a small town and all the negatives surrounding it, it is an absolutely wonderful experience," Moja said.

Moja was born in Pretoria and grew up in Garankuwa as the second eldest of five children. "That was nothing special. I was not the eldest and I wasn't the youngest," she quipped. She had two younger brothers, one of whom died in a car accident and then two sisters.

She went to school in Pretoria and her first contact with the Free State was when she wrote her matric at Moroka High School in Thaba Nchu. "That was one of the best schools for us at that time," she says. After completing matric, she went on to study medicine in KwaZulu-Natal.

In 1982 she returned "home" and completed her internship at the Garankuwa Hospital. Hereafter she specialised in gynaecological obstetrics at Medunsa.

She became the head of the gynaecological obstetrics unit and later opened a branch in Pietersburg.

"This was just about the most heart-rending time of my life. You saw people travelling for up to three days just to see a doctor," she says. "Here we really interacted with the community."

In 2001 she was invited by the University of the Free State to apply for the job of vice-dean of the Faculty of Health Science. "I wasn't too keen," she says, "but they kept on calling to find out if I had applied or not," she says with a smile. "Eventually I gave in and was appointed."

She thought she would work a couple of years under Prof. Kerneels Nel, then the dean of the faculty. "Unfortunately that was not to be. I had hoped that I could learn from him," Moja says.

Prof. Nel died of a heart attack in 2003 after which Moja deputised for him before being appointed as dean.

"This brought along a whole newset of challenges," she says, "Now I have to work out budgets and I need to know what human resources are," she jokes. This has prompted her to take up her studies again and she is currently doing her MBA.

"It has certainly been a challenge to go into management and without my support structure I most certainly wouldn't have been able to do it," Moja says.

Moja is actively involved in her church and serves on various committees including the Health Professional Council where she is acting president of the Medical and Dental Board and the Provincial Aids Council.

To her no job is menial. She recalls when she used to have "high tea" with her staff in Gauteng and Limpopo. "One of the cleaning ladies used to think her job was menial. That is just not so. No hospital can do without even the lowest position. Imagine stepping over rubbish while you're trying to catch a baby. To me everybody is important no matter what you do. "

Moja's eldest daughter is studying for her B.Accounting degree at Wits . Her youngest daughter is in Gr. 9 at Eunice and she has also brought along her niece, who is in Gr. 8 at Eunice. "You see, we need to be three girls in the house."
She feels honoured to have been nominated by the institution especially as it is traditionally male-dominated. "It is not about me, but about the support structure. Nobody can do it on their own. It is a team effort."
BLOEMNUUS - VRYDAG 9 JULIE 2004

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