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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.

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.

Grade:11

1 Answers

ahmad areej
13 Points
5 years ago
threshold frquency = Energy(in Joules)/plank’s constant.
                               =1.9*1.6*10^-19/6.626*10^-34 
                               =4.587*10^14
threshold wavelength = c/threshhold frequency
                                   =3*10^8/4.587*10^14
                                   =6540 * 10^-10
K.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 * 10^6/1.67
v^2 =40.1197 * 10^6
 v   =1290 m/s 

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