Ever wondered what is the colour of a shadow in sunlight ? At first we may think either black or grey as the answer, but that is NOT TRUE! There was a recent article in Physics Education titled "What colour is a shadow?" which proves that in bright sunlight, the dominant colour of a shadow is BLUE ! Although this fact may be non-trivial to our eyes, the author of this paper proves this by the following experiment :He takes a digital photograph of a white sheet of paper in sunlight and shadow, and further analyzes them using a shareware called ImageJ(which is free to download). He quantifies the pixel intensity of the RED, GREEN and BLUE, and finds that 50% of the light intensity constitutes blue colour.
It is a simple and elegant experiment, and reveals an interesting fact....shadows have their colour blue !
Hello Pavan - Great activity yaar - always wanted to be part of such an activity...can u send me the article about shadows? i feel that the blue color is because of its wavelength. among the basic colors, the one wiht shortest wavelength is blue - could this result in it being diffracted by the edges of the paper sheet? would love to get my hands on thsi article....
ReplyDeleteYes, part of the reason is the wavelenght too, but what comes as a surprise is that the ratio of intensities for different RGB colours...
ReplyDeleteThe diffraction from edges has been taken care and I doubt it has effect in this experiment as it was performed on a large area of a A4 paper,and the edges constitute a small percent of the whole structure
Hey P1
ReplyDeleteI wish paper was blocking whole spectrum and was not a poor blue filter :(
or there was no poor PL effect?
I shall check this article on web :)
yes Kabra ji, the experiment reports it as plain A4 paper, whose colour contrast also has to be taken into consideration
ReplyDelete