What colour is a shadow?

Hughes, Stephen William (2009) What colour is a shadow? Physics Education, 44(3), pp. 292-295.

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What colour is a shadow? Black, grey, or some other colour? This paper describes how to use a digital camera to test the hypothesis that a shadow under a clear blue sky has a blue tint. A white sheet of A4 paper was photographed in full sunlight and in shadow under a clear blue sky. The images were analysed using a shareware program called ImageJ. The average red, green and blue pixel values in a region of interest drawn on a photo of the paper in sunlight and shadow were 0.3, 0.32, 0.38 and 0.2, 0.3, 0.5 respectively, demonstrating that a shadow under a blue sky has a blue tint. The experiment would be a useful exercise for a science class.

Impact and interest:

1 citations in Scopus
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ID Code: 20239
Item Type: Journal Article
Refereed: Yes
Additional URLs:
Keywords: shadow, digital camera, RGB, colour ratio, ImageJ
DOI: 10.1088/0031-9120/44/3/009
ISSN: 0031-9120
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
Past > Schools > School of Physical & Chemical Sciences
Copyright Owner: Copyright 2009 Stephen W. Hughes
Deposited On: 30 Apr 2009 02:46
Last Modified: 29 Feb 2012 14:08

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