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Explainphotoelectric effect. |
Answer» Solution :Photoelectriceffect : Electrons(roelectriccurrent )wereejected whencertain metals(for examplepotassium rubidiumcaesium etc) wereexposedto abeam oflight . Thephenomenon is calledphotoelectriceffect.  Light of aparticularfrequencystrikes a cleanmetalsurfaceinsidea vacuumchamberElectronsare ejected from themetaland arecountedby adetectorthatmeasurestheir kineticenergy. Experimentalresults andassumption : (i) Theelectronsareejected FROMTHE metalsurfaceas soonas thebeamof ligthstrikesthe surface Assumption :Thereis no time lgbetween thestrikingof lightbeamand theejectionofelectrionfromthe METALSURFACE Assumption : (number of electron `prop` INTENSITY (III) Thresholdfrequency: Thereis a characteristicminimumfrequency`v_(0)` belowwhichphotoelectriceffectis notobservedis Assumption : Below`v_(0)`photoelectriceffect iscome outwithcertainkineticenergyThekineticenergiesof theseelectronsincreasewith theincreaseof frequencyof the lightused. Exampleof thresholdenergy Red light `(v= 4.3xx 10^(4) Hz)`of anybrightness(intensity )mayshineon apieceof potassium metal forhoursbut notphotoelectronsare ejected. Averyweakyellowlight `(v=5.1 ` to `5.2 XX 10^(4))` photoelectriceffectis observed. Thethresholdfrequency `(v_(0))` forpotassiummetalis`5.0 xx 10^(4)Hz` Note : Theenergycontentof thebeamof lightnumberof electricejecteddoesdependupon the brightnessof lightthe kineticenergyof the ejectedelectronsdoesnot. |
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