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Why interference pattern cannot be seen when a pin hole of young's double slit experiment is illuminated by two identical but separate sodium sources? Explain. |
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Answer» The wavelengths of red (620–750 nm) and blue (450–495 nm) light are less than 67% apart, so that a screen with TWO slits (with the distance between the slits comparable to those wavelengths) can serve for both of the two beams, even simultaneously. If performed simultaneously, each of the two beams will form its own pattern of alternating bright/dark fringes, one superposed over the other. Since the distance between the fringes is proportional to the wavelength, the distance between the bright-red fringes will be 25–67% bigger (depending on which particular wavelengths are present in your “red” and “blue” beams) than the distance between the bright-blue fringes. The color of the overlap between them should be bright-magenta, owing to so-called “additive color mixing.” Wikipedia has a figure [File:Double SLIT interference.png - Wikipedia] showing the result with “WHITE light,” i.e., all colors of the rainbow, not just red and blue. |
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