Thomas Young’s investigations in gradient-index optics

Purpose: James Clerk Maxwell is usually recognized as being the first, in 1854, to consider using inhomogeneous media in optical systems. However, some fifty years earlier Thomas Young, stimulated by his interest in the optics of the eye and accommodation, had already modeled some applications of gradient-index optics. These applications included using an axial gradient to provide spherical aberration-free optics and a spherical gradient to describe the optics of the atmosphere and the eye lens. We evaluated Young’s contributions. Method: We attempted to derive Young’s equations for axial and spherical refractive index gradients. Raytracing was used to confirm accuracy of formula. Results: We did not confirm Young’s equation for the axial gradient to provide aberration-free optics, but derived a slightly different equation. We confirmed the correctness of his equations for deviation of rays in a spherical gradient index and for the focal length of a lens with a nucleus of fixed index surrounded by a cortex of reducing index towards the edge. Young claimed that the equation for focal length applied to a lens with part of the constant index nucleus of the sphere removed, such that the loss of focal length was a quarter of the thickness removed, but this is not strictly correct. Conclusion: Young’s theoretical work in gradient-index optics received no acknowledgement from either his contemporaries or later authors. While his model of the eye lens is not an accurate physiological description of the human lens, with the index reducing least quickly at the edge, it represented a bold attempt to approximate the characteristics of the lens. Thomas Young’s work deserves wider recognition.

Tax and equality in 1972: The case of Lodge v FCT

This paper is part of a larger project described at http://www.law.uq.edu.au/australian-feminist-judgments-project as follows: This project draws its inspiration from two significant recent developments in law and feminist scholarship. The first has been the emergence in Canada and the UK of feminist judgment-writing projects, in which feminist academics, lawyers and activists have written alternative judgments in a series of legal cases, imagining the different decision that might have been made by a feminist judge hearing the case. The second has been the incremental shift in recent years in the number of women judges and Magistrates presiding in courts and tribunals throughout Australia. As part of this project, a group of scholars will write alternative feminist judgments. This paper is one of the alternative feminist judgements. The case used for this discussion is Lodge v Federal Commissioner of Tax [1972] HCA 49. In that case, a woman, earning income by way of commission in her occupation as a law costs clerk, which she carried out at her home, claimed to deduct from her assessable income child care fees that enabled her to devote time and attention to her work. The High Court held that no right to a deduction had arisen. It found that, although the purpose of the expenditure was for gaining assessable income, it did not take place in, or in the course of, preparing bills of cost. Further, the expenditure was of a ‘private or domestic’ nature. This seminal taxation decision, which prevents deductions for childcare, has broad financial ramifications for workers in the home and those with childcare responsibilities. It designates childcare duties as ‘private’, notwithstanding the need for these in order, particularly for women, to work in the public sphere.