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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 hikers to Cape Town reflect on their journey

2014-05-26

For the four volunteers from the university who are currently on their way to the Cape on foot, every hour of every day is a victory.

It is three weeks since two employees from the University of the Free State (UFS), Adéle van Aswegen and Ntokozo Nkabinde, together with two other Bloemfontein residents, Nico Piedt and Ronel Warner, left Bloemfontein on fóót for the Cape, in order to highlight the problem of food insecurity among students.

On Sunday 18 May they crossed the halfway mark at Beaufort West and will conclude their journey on Tuesday 3 June in Cape Town.

This is what the hikers have to say after three weeks on the road:

Adéle van Aswegen
It isn’t only a physical journey, but rather an emotional journey you undertake. You learn what it means to be truly thankful for basic things like clothes, a place to sleep and food.

Nico Piedt
I know what it feels like to survive on only a glass of water in your stomach – a cup of weak tea if you’re lucky – for the whole day. If I can help (through the hike) to give someone a better chance in life, then it is worthwhile.

Ronel Warner
You think and grow simultaneously. As you plan every stride ahead of you, you also plan your life ahead.

Ntokozo Nkabinde
You don’t walk for yourself. You undertake this journey, maybe because you want to help someone, but this journey is actually in honour of something bigger and you just have to endure.”

These boots are made for walking ... to Cape Town (Article of 02 May 2014)
“Aren’t auntie and them hungry yet?” Country folk worried about NSH hikers (15 May 2014)

Daily updates:
(You can also follow us on @UFSweb for daily tweets)

Day 33: 2 June 2014
13:40
20 km
Sunset Beach, Cape Town

Day 32: 1 June 2014
16:05
26 km
Mervyn and Sanet Wessels, Belville

Day 31: 31 May 2014
16:31
39.6 km
Rhonell and Gavin Julain, Paarl

Day 30: 30 May 2014
14:00
16 km
Monte Rosa, Rawsonville

Day 29: 29 May 2014
13:16
31 km
The Habit, Worcester

Day 28: 28 May 2014
11:00
22.4 km
Monte Roza, De doorns

Day 27: 27 May 2014
17:00
21.1 km
Karoo Hotel

Day 26: 26 May 2014
18:27
43.3 km
Tows river

Day 25: 25 May 2014
12:18
Lord Milner Hotel, Matjiesfontein

Day 24: 24 May 2014
16:30
42 km
Laingsburg Country Lodge

Day 23: 23 May 2014
17:32
41.8 km
Vergenoeg

Day 22: 22 May 2014
16:42
43 km
Assendelft Lodge and Bush Camp, Prins Albert

Day 21: 21 May 2014
15:09
42 km
Leeu Gamka Hotel

Day 20: 20 May 2014
13:39
20 km
Alida, Springfontein

Day 19: 19 May 2014
12:31
27.6 km
Teri Moja Game Lodge

Day 18: 18 May 2014
First rest day
Nagenoeg Guesthouse, Beaufort West

Day 17: 17 May 2014
19:30
62.3 km
Nagenoeg Guesthouse, Beaufort West

Day 16: 16 May 2014
13:00
14 km
Taaibochfontein

Day 15: 15 May 2014
16:03
32 km
Travalia, Three Sisters

Day 14: 14 May 2014
18:33
43 km
Joalani Guest Farm

Day 13: 13 May 2014
17:30
33 km
Die Rondawels

Day 12: 12 May 2014
16:49
40 km
Aandrus B&B in Richmond

Day 11: 11 May 2014
39 km
Wortelfontein (Magdel and Christiaan)

Day 10: 10 May 2014
15:44
34 km
Hanover Lodge

Day 9: 09 May 2014
40.8 km
Camping between Colesberg and Hanover

Day 8: 08 May 2014
15:25
33.7 km
Colesberg, The Lighthouse Guesthouse

Day 7: 07 May 2014
15:08
23 km
Orange River Lodge

Day 6: 06 May 2014
15:57
51.06 km
Gariep Forever Resort

Day 5: 05 May 2014
12:18
28 km
Rondefontein

Day 4: 04 May 2014
15:27
35 km
Trompsburg: Fox Den

Day 3: 03 May 2014
17:30
46.74 km
Edenburg Country Lodge (Hotel)

Day 2: 02 May 2014
11:44 am
15.3 km
Tom's Place

Day 1: 01 May 2014
32 km
Leeuwberg

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