Teaching about Waves with Applications in Lenses

The paper examines ways of teaching wave pulses traveling on strings and wave fronts in two dimensional waves. The phenomena examined for pulses are: reflection, transmission and superposition. Two methods of finding the refracted wave fronts, the corresponding rays and the refraction angle are presented. Then the gradual change of the speed of propagation of a wave is presented. In the last part is examined the application of the concept of wave fronts in lenses and Huygens’ method of finding the shape of a perfect lens. The students’ difficulties with connection with all these subjects are presented.

Metamaterial Lensing Devices

In recent years, the development of metamaterials and metasurfaces has drawn great attention, enabling many important practical applications. Focusing and lensing components are of extreme importance because of their significant potential practical applications in biological imaging, display, and nanolithography fabrication. Metafocusing devices using ultrathin structures (also known as metasurfaces) with superlensing performance are key building blocks for developing integrated optical components with ultrasmall dimensions. In this article, we review the metamaterial superlensing devices working in transmission mode from the perfect lens to two-dimensional metasurfaces and present their working principles. Then we summarize important practical applications of metasurfaces, such as plasmonic lithography, holography, and imaging. Different typical designs and their focusing performance are also discussed in detail.

Prohibition and ‘Sharab’ as Political Protest in Karachi

This chapter by Nadeem Farooq Paracha brings oral history and memoir to the fore. Paracha interweaves national, social and personal histories in an extraordinary analysis of how alcohol, its sale and consumption, became intrinsic to Karachi’s leftist political culture in the euphoria of the post-Zia years; how political rebellion involving alcohol fueled violence on Karachi’s student campuses; and shaped Paracha’s personal nemesis and life trajectory into journalism rather than militancy. The adage that the ‘personal is political’ acquires enriched meaning in these unfoldings of a simultaneously painful, exhilarating, and destructive era that shaped one radical element of the city’s political commentariat. The politics surrounding alcohol from 1970-90 offer a perfect lens, Paracha shows us, onto transformations of religion, morality, and revolution within student support for the Pakistan People’s Party in a saturnalian urban setting.