{"title":"Extended versus point light source: where does the difference in the illuminance exist?","authors":"V. Ivchenko","doi":"10.31349/revmexfise.18.127","DOIUrl":null,"url":null,"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.","PeriodicalId":49600,"journal":{"name":"Revista Mexicana De Fisica E","volume":"12 1","pages":"127-130"},"PeriodicalIF":0.0000,"publicationDate":"2021-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Revista Mexicana De Fisica E","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.31349/revmexfise.18.127","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"Social Sciences","Score":null,"Total":0}
引用次数: 0
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.
期刊介绍：
The Revista Mexicana de Física (Rev. Mex. Fis.) publishes original papers of interest to our readers from the physical science com unity. Language may be English or Spanish, however, given the nature of our readers, English is recommended. Articles are classified as follows:
Research. Articles reporting original results in physical science.
Instrumentation. Articles reporting original contributions on design and construction of scientific instruments. They should present new instruments and techniques oriented to physical science problems solutions. They must also report measurements performed with the described instrument.
Reviews. Critical surveys of specific physical science topics in which recent published information is analyzed and discussed. They should be accessible to physics graduate students and non specialists, and provide valuable bibliography to the specialist.
Comments. Short papers (four pages maximum) that assess critically papers by others authors previously published in the Revista Mexicana de Física. A comment should state clearly to which paper it refers.
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