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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 research sheds light on service delivery protests in South Africa

2015-01-23

UFS research sheds light on service delivery protests in South Africa

Service delivery protests in the country have peaked during 2014, with 176 major service delivery protests staged against local government across South Africa.

A study by the University of the Free State (UFS) found that many of these protests are led by individuals who previously held key positions within the ANC and prominent community leaders. Many of these protests involved violence, and the destruction had a devastating impact on the communities involved.

This study was done by Dr Sethulego Matebesi, researcher and senior lecturer at the UFS. He focused his research on the dynamics of service delivery protests in South Africa.

Service delivery protests refer to the collective taken by a group of community members which are directed against a local municipality over poor or inadequate provision of basic services, and a wider spectrum of concerns including, for example, housing, infrastructural developments, and corruption.

These protests increased substantially from about 10 in 2004 to 111 in 2010, reaching unprecedented levels with 176 during 2014.

The causes of these protests are divided into three broad categories: systemic (maladministration, fraud, nepotism and corruption); structural (healthcare, poverty, unemployment and land issues); and governance (limited opportunities for civic participation, lack of accountability, weak leadership and the erosion of public confidence in leadership).

In his research, Dr Matebesi observed and studied protests in the Free State, Northern Cape and the North-West since 2008. He found that these protests can be divided into two groups, each with its own characteristics.

“On the one side you have highly fragmented residents’ groups that often use intimidation and violence in predominantly black communities. On the other side, there are highly structured ratepayers’ associations that primarily uses the withholding of municipal rates and taxes in predominantly white communities.”

Who are the typical protesters?

Dr Matebesi’s study results show that in most instances, protests in black areas are led by individuals who previously held key positions within the ANC - prominent community leaders. Generally, though, protests are supported by predominantly unemployed, young residents.

“However, judging by election results immediately after protests, the study revealed that the ANC is not losing votes over such actions.”

The study found that in the case of the structured ratepayers’ associations, the groups are led by different segments of the community, including professionals such as attorneys, accountants and even former municipal managers.

Dr Matebesi says that although many protests in black communities often turned out violent, protest leaders stated that they never planned to embark on violent protests.

“They claimed that is was often attitude (towards the protesters), reaction of the police and the lack of government’s interest in their grievances that sparked violence.”

Totally different to this is the form of peaceful protests that involves sanctioning. This requires restraint and coordination, which only a highly structured group can provide.

“The study demonstrates that the effects of service delivery protests have been tangible and visible in South Africa, with almost daily reports of violent confrontations with police, extensive damage to property, looting of businesses, and at times, the injuring or even killing of civilians. With the increase of violence, the space for building trust between the state and civil society is decreasing.”

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