Light of frequency 7.21 times 10^{14} ; Hz is | vedclass

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Question

(A) Given: Frequency of incident light $
u = 7.21 	imes 10^{14} \; Hz$,maximum speed of electrons $v = 6.0 	imes 10^{5} \; m/s$,mass of electron $m

Vedclass · Accepted Answer

$4.73 	imes 10^{14} \; Hz$

Vedclass · Answer

(A) Given: Frequency of incident light $
u = 7.21 	imes 10^{14} \; Hz$,maximum speed of electrons $v = 6.0 	imes 10^{5} \; m/s$,mass of electron $m = 9.11 	imes 10^{-31} \; kg$,and Planck's constant $h = 6.626 	imes 10^{-34} \; J \cdot s$.According to Einstein's photoelectric equation: $K_{max} = h
u - h
u_0$,where $K_{max} = \frac{1}{2}mv^2$.Substituting the values: $\frac{1}{2} 	imes (9.11 	imes 10^{-31}) 	imes (6.0 	imes 10^5)^2 = (6.626 	imes 10^{-34}) 	imes (7.21 	imes 10^{14} - 
u_0)$.$1.6398 	imes 10^{-19} = (6.626 	imes 10^{-34}) 	imes (7.21 	imes 10^{14} - 
u_0)$.$2.4748 	imes 10^{14} = 7.21 	imes 10^{14} - 
u_0$.$
u_0 = 7.21 	imes 10^{14} - 2.4748 	imes 10^{14} = 4.7352 	imes 10^{14} \; Hz$.Thus,the threshold frequency is approximately $4.73 	imes 10^{14} \; Hz$.

Light of frequency $7.21 \times 10^{14} \; Hz$ is incident on a metal surface. Electrons with a maximum speed of $6.0 \times 10^{5} \; m/s$ are ejected from the surface. What is the threshold frequency for photoemission of electrons?

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