A certain metal in the photoelectric effect experiment has a work function of 2.

Question

A certain metal in the photoelectric effect experiment has a work function of 2.3 ev. For a given experiment, the maximum kinetic energy of the ejected electrons is 1.6 eV. 17) What is the wavelength of the incident photons? 218 nm. 18) What is the DeBroglie wavelength of the ejected electrons? 19) What is the maximum length of photo that would eject electrons from this metal? a) 339 nm 432 nm d 639 nm e) 739 nm 20) If the intensity of light was increased, how would the above answer change? a) it would increase would decrease would stay the same

Explanation / Answer

work function W =2.3 eV
Kmax = 1.6 eV
17)
from the einstien relation
E = W + Kmax
E = 3.9 eV
hc/L = 3.9x1.6x10^-19
wavelenght L = 6.625x10^-34*3x10^8/(3.9x1.6x10^-19 ) =317.9 nm = 318 nm
b) 318 nm
18)
debroglie wavelenght of the electron L =h/sqrt(2mK)
L =6.625x10^-34/sqrt(2*9.1x10^-31*1.6*1.6*10^-19) = 0.97 x 10^-9 = 0.97 nm
19)
minimum energy needed to eject the electrons is called as work function
corresponding to maximum wavelenght
L =hc/W = 6.625x10^-34*3x10^8/(2.3*1.6x10^-19) = 539 x10^-9 m = 539 nm
c) 539 nm
photo electric effect does not depend on intensity of incident light , it only depends on incident energy
c)
it would stay the same

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