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18 April 2022 | Story Leonie Bolleurs | Photo Stephen Collett
Prof Ted Kroon
Prof Ted Kroon from the Department of Physics recently delivered his inaugural lecture on the topic What’s the use of a rainbow on the UFS Bloemfontein Campus.

“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

Bloemfontein's quality of tap water compares very favourably with bottled water
2009-08-04

The quality of the drinking water of five suburbs in Bloemfontein is at least as good as or better than bottled water. This is the result of a standard and chemical bacterial analysis done by the University of the Free State’s (UFS) Centre for Environmental Management in collaboration with the Institute for Groundwater Studies (IGS).

Five samples were taken from tap water sources in the suburbs of Universitas, Brandwag, Bain’s Vlei, Langenhoven Park and Bayswater and 15 samples were taken of different brands of still and unflavoured bottled water. The samples were analysed at the laboratory of the IGS, while the interpretation of the analysis was done by the Centre for Environmental Management.

“We wanted to evaluate the difference in quality for human consumption between tap water and that of the different brands of bottled water,” said Prof. Maitland Seaman, Head of the Centre for Environmental Management.

“With the exception of two samples produced by multinational companies at their plants in South Africa, the different brands of bottled water used for the study were produced by South African companies, including a local small-scale Bloemfontein producer,” said Prof. Seaman.

According to the labels, the sources of the water vary from pure spring water, to partial reverse osmosis (as an aid to standardise salt, i.e. mineral, content), to only reverse osmosis (to remove salts). (Reverse osmosis is a process in which water is forced under pressure through a pipe with minute pores through which water passes but no – or very low concentrations of – salts pass.)

According to Prof. Seaman, the analysis revealed some interesting findings, such as:

• It is generally accepted that drinking water should have an acceptable level of salt content, as the body needs salts. Most mineral contents were relatively higher in the tap water samples than the bottled water samples and were very much within the acceptable range of drinkable water quality. One of the bottled samples, however, had a very low mineral content, as the water was produced by reverse osmosis, as stated on the bottle. While reverse osmosis is used by various producers, most producers use it as an aid, not as a single method to remove nearly all the salts. Drinking only such water over a prolonged period may probably have a negative effect on the human physiology.

• The pH values of the tap water samples (8,12–8,40) were found to be slightly higher (slightly alkaline), like in all south-eastern Free State rivers (from where the water is sourced) than the pH of most of the bottled water samples, most of which are sourced and/or treated in other areas. Two brands of bottled water were found to have relatively low pH levels (both 4,5, i.e. acidic) as indicated on their bottles and as confirmed by the IGS analysis. The health implication of this range of pH is not significant.

• The analysis showed differences in the mineral content given on the labels of most of the water bottles compared to that found by IGS analysis. The possibility of seasonal fluctuation in content, depending on various factors, is expected and most of the bottling companies also indicate this on their labels. What was a rather interesting finding was that two pairs of bottled water brands claimed exactly the same mineral content but appeared under different brand names and were also priced differently. In each case, one of the pair was a well-known house brand, and the other obviously the original producer. In one of these paired cases, the house brand stated that the water was spring water, while the other (identical) “original” brand stated that it was spring water treated by reverse osmosis and oxygen-enriched.

• Nitrate (NO3) levels were uniformly low except in one bottled sample, suggesting a low (non-threatening) level of organic pollution in the source water. Otherwise, none of the water showed any sign of pollution.

• The bacterial analysis confirmed the absence of any traces of coliforms or E.coli in any of the samples, as was also indicated by the bottling companies. This is very reassuring. What is not known is how all these waters were sterilised, which could be anything from irradiation to chlorine or ozone treatment.

• The price of the different brands of bottled water, each containing 500 ml of still water, ranged between R3,99 and R8,99, with R5,03 being the average price. A comparison between the least expensive and the most expensive bottles of water indicated no significant difference in quality. In fact, discrepancies were observed in the most expensive bottle in that the amount of Calcium (Ca) claimed to be present in it was found to be significantly different from what the analysis indicated (29,6 mg/l versus 0,92 mg/l). The alkalinity (CaCO3 mg/l) indicated on the bottle was also found to differ considerably (83 mg/l versus 9,4 mg/l). The concentration of Total Dissolved Salts (TDS) was not given on the product.

“The preference for bottled water as compared to Bloemfontein’s tap water from a qualitative perspective as well as the price discrepancy is unjustifiable. The environmental footprint of bottled water is also large. Sourcing, treating, bottling, packaging and transporting, to mention but a few of the steps involved in the processing of bottled water, entail a huge carbon footprint, as well as a large water footprint, because it also requires water for treating and rinsing to process bottled water,” said Prof. Seaman.

Media Release
Lacea Loader
Deputy Director: Media Liaison
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: loaderl.stg@ufs.ac.za  
3 August 2009

 

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