The work function of metallic rubidium is 2.09 eV. What is the minimum wavelengt

Question

The   work  function  of metallic  rubidium  is  2.09  eV. What  is  the   minimum wavelength of  light  required  to  observe  the photoelectric   effect on  rubidium?  If light with a 170-nm wavelength is absorbed by the surface, what is the speed of the emitted electrons? The   work  function  of metallic  rubidium  is  2.09  eV. What  is  the   minimum wavelength of  light  required  to  observe  the photoelectric   effect on  rubidium?  If light with a 170-nm wavelength is absorbed by the surface, what is the speed of the emitted electrons?

Explanation / Answer

1.

from energy balance;

K.E=hc/lambda-work function

For just to observe photoelectric effect ;

hc/lambda-work function=0

or

lambda=(6.63*10^-34*3*10^8)/2.09*1.6*10^-19=594.79nm

2.

now, for lambda=170nm

K.E=hc/lambda-work function

or

K.E=(6.63*10^-34*3*10^8)/(170*10^-9)-2.09*1.6*10^-19

or

K.E=8.356*10^-19 J

or

0.5mv^2=9.61*10^-19 J

or

v=1339798.15m/s

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