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Ultraviolet light of wavelength 280 nm is used in an experiment on photoelectric effect with lithium ( varphi = 2.5 eV) cathode. Find (a) the maximum kinetic energy of the photoelectrons and (b) the stopping potential. |
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Answer» Solution : (a) The maximum kinetic energy is ` K_max = (hc/lambda)- varphi. ` `= (1242 eV nm/ 280 nm)- 2.5 eV. ` ` = 4.4 eV - 2.5 eV = 1.9eV. ` (B) STOPPING potential V is given by ` eV= K_max` ` or, V=(K_max)/E = 1.9 eV/e = 1.9 V.` |
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