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From darkness to light

Photo: Special Arrangement

Photo: Special Arrangement   | Photo Credit: Deepak Davda

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The physics Olympiad differs in nature from other exams such as the JEE or the Boards.

The International Physics Olympiad (IPHO2015) was held in Mumbai this year, from July 8-12. There were about 382 students participating, representing 83 countries from all over the globe. As the host, India was responsible for making the local arrangements and also setting a physics test of appropriate level and interest for students at the high school level.  The student teams were accompanied by their team leaders and observers, and the scale of the event made the organisation a formidable challenge. For over a year and a half, the Homi Bhabha Centre at Mumbai has worked to meet this challenge. The experimental test this year dealt with light as a probe of matter. This was an appropriate choice in 2015, the International Year of Light. Light is a wave, and when it is incident on objects of size similar to its wavelength, undergoes delicate diffraction effects that reveal the structure of the object being probed.   

In the first part of the experiment, the students were asked to do an experiment inspired by Rosalind Franklin’s study using X-ray diffraction, which revealed the double-helical structure of DNA. In the simplified student version, X-rays are replaced by light and the double helix by mechanical springs.  In the second part, there was an analogue of a crystal lattice constructed by tiny ripples on the surface of water. 

The first theoretical task was, ‘Understanding the Sun’. The Sun puts out energy in the form of light and also some less familiar forms like neutrinos. The problem starts by using the light emitted by the Sun to learn about the temperature at the surface of the Sun. Next we learn how to harvest the energy put out by the Sun, using semiconductor physics. Finally, we realise that the elusive neutrino permits us to look deep into the interior of the Sun, just as X-rays are used by doctors to see our bones. This enquiry brings us abreast with current research in the Standard model of particle physics.

The second task was to do with variational principles in physics. This is an idea with a long and illustrious history, dating back to Hero of Alexandria and traversing the centuries through Fermat, Maupertuis, Hamilton and Feynman. This is an advanced idea that threads between optics, classical mechanics and Schrodinger’s wave mechanics. The challenge for us was to bring it to the level where it can be appreciated by school students.

The first two problems were mainly concerned with fundamental aspects of physics. The third problem was more applied, dealing the design of nuclear reactors. For safe operation, a reactor has to be designed so that energy is released in a controlled fashion. The task for the student was to carry out the design. We hope that the students enjoyed solving the problems as much as we enjoyed setting them.

The writer is chairperson of the Academic Committee of IPhO 2015.

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Printable version | Dec 9, 2019 11:38:24 AM | https://www.thehindu.com/features/education/from-darkness-to-light/article7438238.ece

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