Extended versus point light source: where does the difference in the illuminance exist?

Authors

  • V. Ivchenko Kherson State Maritime Academy

DOI:

https://doi.org/10.31349/RevMexFisE.18.127

Keywords:

illuminance, luminous ball, disc and line .point light source, inverse square law

Abstract

In this paper we derive and analyse the expressions to find the illuminance from luminous ball, disc and line in the case of general position of the light receiver. We show that one can always replace a luminous ball with a point light source located at its center and having the appropriate luminous intensity. Any luminous disc or line can be considered, with reasonable accuracy (the relative error in the determination of the illuminance is less than $5 \%$), as the point light source with anisotropic (cosine) luminous intensity and placed at their center, if the distance to the observation point is approximately four times larger than their characteristic sizes. The issues outlined in this article will be useful for undergraduate students, who study the basics of photometry.

References

Bukshtab M., Photometry, Radiometry, and Measurements of Optical Losses (Singapore: Springer Singapore 2019), p 13

Zumtobel Sta, The Lighting Handbook (Zumtobel Lighting GmbH, 2018), ch. 2

Murdoch Joseph B. 1981 Inverse square law approximation of illuminance J. Illum. Eng. Soc. 10 (2) 96-106 10

McCluney W R, McCluney R, Introduction to Radiometry and Photometry (Boston London: Artech House 1994), p 11-15

Rea Mark S., IESNA Lighting Handbook (Illuminating Engineering, 2000), ch 9

Bass M, Handbook of Optics, Volume II: Design, Fabrication and Testing, Sources and Detectors, Radiometry and Photometry (New-York: McGraw-Hill Professional 2009), p 24.10

Walker M J and Steadman F M 1947 The treatment of extended light sources in elementary textbooks Am. J. Phys. 15 (1) 65-67

Downloads

Published

2021-01-04

How to Cite

[1]
V. Ivchenko, “Extended versus point light source: where does the difference in the illuminance exist?”, Rev. Mex. Fis. E, vol. 18, no. 1 Jan-Jun, pp. 127–130, Jan. 2021.

Issue

Vol. 18 No. 1 Jan-Jun (2021): Revista Mexicana de Física E

Section

02 Education in Physics

License

Copyright (c) 2021 Vladimir Valerievich Ivchenko

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Authors retain copyright and grant the Revista Mexicana de Física E right of first publication with the work simultaneously licensed under a CC BY-NC-ND 4.0 that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.