Life Processes Class 10 Notes Science Chapter 6
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Wave-Particle Duality
The interference phenomena demonstrated by the work of Young, Fresnel and others in the early 19th Century, apparently settled
the matter that light was a wave phenomenon, contrary to the views of Newton a century earlier--case closed! But nearly a century
later, phenomena were discovered which could not be satisfactorily accounted for by the wave theory, specifically blackbody
radiation and the photoelectric effect.
Deviating from the historical development, we will illustrate these effects by a modification of the double slit experiment. Let us
equip the laser source with a dimmer switch capable of reducing the light intensity by several orders of magnitude, as shown in
Figure . With each successive filter the diffraction pattern becomes dimmer and dimmer. Eventually we will begin to see
localized scintillations at random positions on an otherwise dark screen. It is an almost inescapable conclusion that these
scintillations are caused by photons, the bundles of light postulated by Planck and Einstein to explain blackbody radiation and the