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The work function for caesium atom is 1.9eV. calculate the threshold wavelength and the threshold frequency of the radiation. If the caesium element is irradiated with a wavelength 500nm,calculate the kinetic energy and the velocity of the ejected photoelectron.
threshold frquency = Energy(in Joules)/plank’s constant. =1.9*1.6*10^-19/6.626*10^-34 =4.587*10^14threshold wavelength = c/threshhold frequency =3*10^8/4.587*10^14 =6540 * 10^-10K.E = Energy total – work function = (6.626*3*10^-26)/500 *10^-9 – (1.9*1.6*10^-19) = 0.335 * 10^-19 = 335*10^-22 v^2 = 2*K.E/m =2* 335*10^-22/1.67*10^-27 =670 * 10^5?1.67 = 67 * 10^6/1.67v^2 =40.1197 * 10^6 v =1290 m/s
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