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Dependence of Shadow Sizes on Various Variables
New Phys.: Sae Mulli 2019; 69: 1053~1063
Published online October 31, 2019;
© 2019 New Physics: Sae Mulli.

Taekyu KIM*

Department of Science Education, Jeonju National University of Education, Jeonju 55101, Korea
Correspondence to:
Received July 22, 2019; Revised September 3, 2019; Accepted September 11, 2019.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
The shadow sizes of a plane object according to the movement of a point light source are equal to the shadow sizes according to the movement of an object and the movement of a screen. Also, its shadow sizes are proportional to the product of the shadow-size changes with object and screen movements. As the ration of the radius of the spherical object to the object distance from the light source increases, the relative error in the shadow size for plane objects increases. The sizes of the umbra shadows caused by large spherical light sources decrease as the ratio of the light source size to the object size increases and the ratio of the screen distance to the object distances increases. The penumbra shadow sizes increase with increasing ratios of the light source size to the object size and the screen distance to the object distance. When the light source because point light source, the sizes of the umbra shadow and the penumbra shadow are equal. The shadows of objects caused by plane light source are umbra shadows, and the sizes of these umbra shadows depend only on the size of the object.
PACS numbers: 01.40.Eg
Keywords: Shadow, Spherical Object, Light Source

October 2019, 69 (10)
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