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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

UFS Centenary 2004 / 2005 October (centenary) fest Activities

2004-10-08

Friday, 08 October 2004
17:00 – 24:00
Callie Human Centre, UFS
Macufe Rock Concert
With: Rooibaardt, Karen Zoid, The Narrow, F****polisiekar, Stuurbaard Bakkebaard (from the Netherlands), DJ Bob, Ready D, Neva Me.
Cost : R50-00
Bookings : Pacofs (051-447 7772)

Sunday, 10 October 2004
16:00 – 18:00
Callie Human Centre, UFS
Macufe Three Tenors Concert
With: Phillip Kotze, Chris Coetzer and Du Preez Stolz, as well as Angela Kerrison. Free State Symphony Orchestra conducted by Chris Dowdeswell.
Cost :R60-00 (adults), R40-00 (children, scholars, students and pensioners)
Bookings : Pacofs (051-447 7772)

Tuesday, 12 October 2004
11:00 – 15:00
Centenary Complex, UFS
Inauguration of Centenary Complex
Open day with a variety of musical recitals in different rooms
Cost : Free
Enquiries : Elize Rall (051-401 3382)

15:00 – 17:00
Parking area next to the Centenary Complex, UFS
Kovsie Mosaic Day
Collage of the Century, Dance to the beat, Cultural Cartoon,
Who’s line is it anyway?
Cost : Free
Enquiries : Louis Botha (051-401 2819) or
AC Geldenhuys (084 585 3338)

Wednesday, 13 October 2004
19:00
Centenary Complex, UFS
Première of documentary film : The Life and Legacy of King Moshoeshoe
Note : By invitation only
Enquiries : Elize Rall (051-401 3382)

Thursday, 14 October 2004
18:45 – 21:00
Red Square (in front of Main Building), UFS
Centenary Honorary Doctorate Degree Graduation Ceremony
Conferred on: Me. Antjie Krog, Prof. Jakes Gerwel, Mr. Karel Schoeman, Dr. Frederick van Zyl Slabbert, Prof. Saleem Badat, Dr. Khotso Mokhele, Prof. Robert Bringle, Prof. Leo Quayle, Prof. Jack de Wet, Prof. Kerneels Nel (posthumously), Prof. Boelie Wessels and Prof. Jaap Steyn .
Cost : Free. Please RSVP if you would like to attend.
Enquiries : Elize Rall (051-401 3382)

Friday, 15 October 2004
18:30
Centenary Complex, UFS
Alumni Dinner and Centenary Award Ceremony
Approximately 140 centenary medals will be awarded in acknowledgement of exceptional contributions to the development of the University. The award ceremony is followed by the Alumni dinner in the Callie Human Centre.
Cost : R100-00/person
Enquiries : Elize Rall (051-401 3382)

15:00 (to 12:00, Saturday, 16 October 2004),
UFS campus
Reunion : Momentum Adventure and Expedition Association
Including : Setting up of the Kovsie Momentum base camp, champagne breakfast and abseiling.
Cost : R50-00/person for breakfast
Enquiries : Gerrit van der Merwe (072 4317 153) or
Niel Fraser (082 772 5642)
Website : www.uovs.ac.za/associations/momentum_hrcc.

19:00 (to 11:00 Sunday, 17 October 2004)
Reunion : Cantare Revue Group
Including : Formal dinner, budget show, bring and braai, church service.
Cost : R100-00/person for the dinner
Enquiries : Louis Botha (051-401 2819)

19:00 (to 24:00 Saturday, 16 October 2004
Reunion : House NJ van der Merwe
Including : Senior Student’s Association and concerts
Cost : R5-00/person
Enquiries : Tutu Ntlathi (051-401 4122 / 072 865 2227)

Saturday, 16 October 2004
09:00 – 10:00
Committee Room 120, Faculty of Theology
Founding of Theology Alumni Association
Enquiries: Henna Nel (051-401 2669)

10:00 – 12:00
Parking area, CR Swart Building, UFS
Alumni Campus Tour
Including : Visits to the new physical developments on campus
Cost : Free
Enquiries : Jeanette Jansen (051-401 3594)

10:00 – 12:00
Sonnedou gazellie (next to NJ van der Merwe Residence), UFS
Reunion : Ladies’ Tea
Visit our new gazellie and find out what Sonnedou is up to these days.
Cost : R25-00/person
Enquiries : Anne-Marie Delport (072 109 0507)

12:00 – 16:00
JBM Hertzog Residence (garden in front of Senior Student’s Association), UFS
Reunion : Braai
Cost : Approximately R20-00/person
Enquiries : Hattingh Bornman (084 240 5226)

12:00 Vergeet-my-nie Residence, UFS
Reunion : Braai
Bring and braai. We supply the facilities. Bring old photographs and stories. Enjoy Aunt Juls’ last visit.
Cost : Free
Enquiries : Mari Jordaan (051-444 2832/072 392 4444)

12:00 HF Verwoerd Residence Senior Student’s Association, UFS
Reunion : Spit roast
Cost : R60-00/person
Enquiries : Jan-Chris Landman (051-401 3613 / 082 664 6062)

18:30 Floreat Hall, Bloemfontein Civic Centre (Braam Fisher Building)
Irawa 60 Reunion
For all former editors, former and current main editorial staff and coworkers
Cost : R100-00/person
Enquiries : Sanri van Wyk (072 333 1011)
Elzette Boucher (072 180 6265)

19:00 – 24:00 Red Square (in front of Main Building), UFS
Informal Alumni Reunion
Spit roast and stories in a marquee
Cost : R60-00/person
Enquiries : Elize Rall (051-401 3382)

Sunday, 17 October 2004
10:00 – 11:00
Kovsie Church
Church Service

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