{"id":49,"date":"2021-01-24T19:50:47","date_gmt":"2021-01-25T00:50:47","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/lightingforelectricians\/chapter\/inverse-square-law\/"},"modified":"2021-03-30T18:26:16","modified_gmt":"2021-03-30T22:26:16","slug":"inverse-square-law","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/lightingforelectricians\/chapter\/inverse-square-law\/","title":{"raw":"Inverse Square Law","rendered":"Inverse Square Law"},"content":{"raw":"Put simply, the further an object or surface is from a light source, the less light will hit that object or surface. Seems obvious, but it is worth noting that the level of illumination on a surface drops with the square of the distance.\n\n \n
Expressed as an equation:<\/p>\n
[latex]Illumination (lux) =\\frac{Light-intensity (candela)}{distance^2(m)}[\/latex]<\/p>\nExample 1: If 1 Lux of illumination is measured on a surface that is one meter away from a light source, the illumination would be 1\/4th as bright, or \u00bc Lux two meters away, and 1\/9th as bright, or 1\/9th Lux three meters away.\n\n[caption id=\"attachment_48\" align=\"aligncenter\" width=\"640\"] Illumination of a surface drops with the square of the distance[\/caption]\n\nThis example is a very low value of illumination, but it does illustrate the concept of the inverse square law. A more realistic value of luminous flux density might be around 100 Lux.\n\nExample 2: If 100 Lux of illumination is measured on a surface that is one meter away from a light source, the illumination would be one quarter as bright, or 25 Lux two meters away, and 1\/9th as bright, or 11.1 Lux three meters away, and so on.\n\n","rendered":"
Put simply, the further an object or surface is from a light source, the less light will hit that object or surface. Seems obvious, but it is worth noting that the level of illumination on a surface drops with the square of the distance.<\/p>\n
<\/p>\n
Expressed as an equation:<\/p>\n
<\/p>\n
Example 1: If 1 Lux of illumination is measured on a surface that is one meter away from a light source, the illumination would be 1\/4th as bright, or \u00bc Lux two meters away, and 1\/9th as bright, or 1\/9th Lux three meters away.<\/p>\nIllumination of a surface drops with the square of the distance<\/figcaption><\/figure>\n
This example is a very low value of illumination, but it does illustrate the concept of the inverse square law. A more realistic value of luminous flux density might be around 100 Lux.<\/p>\n
Example 2: If 100 Lux of illumination is measured on a surface that is one meter away from a light source, the illumination would be one quarter as bright, or 25 Lux two meters away, and 1\/9th as bright, or 11.1 Lux three meters away, and so on.<\/p>\n
![\"\"](\"https:\/\/pressbooks.bccampus.ca\/lightingforelectricians\/wp-content\/uploads\/sites\/1349\/2021\/01\/inverse-square-law.png\")
Illumination of a surface drops with the square of the distance[\/caption]\n\nThis example is a very low value of illumination, but it does illustrate the concept of the inverse square law. A more realistic value of luminous flux density might be around 100 Lux.\n\nExample 2: If 100 Lux of illumination is measured on a surface that is one meter away from a light source, the illumination would be one quarter as bright, or 25 Lux two meters away, and 1\/9th as bright, or 11.1 Lux three meters away, and so on.\n\n![\"\"](\"https:\/\/pressbooks.bccampus.ca\/lightingforelectricians\/wp-content\/uploads\/sites\/1349\/2021\/03\/inverse-square-law-ex-2.png\")
","rendered":"![\"Illumination (lux) =\frac{Light-intensity (candela)}{distance^2(m)}\"](\"https:\/\/pressbooks.bccampus.ca\/lightingforelectricians\/wp-content\/ql-cache\/quicklatex.com-b06ca38af14d462c3e5ead7190b32506_l3.png\" "\\"Rendered")
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