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The work function for a certain metal is $4.2 eV$. Will this metal give photoelectric emission for incident radiation of wavelength $589 nm$?

$\begin {array} {1 1} (a)\;Yes & \quad (b)\;No \\ (c)\;Maybe & \quad (d)\;Can't\: be\: determined \end {array}$


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Ans : (b) No
$ \phi_{\circ}=4.2eV$
$ \lambda=589\: nm = 589 \times 10^{-9} m$
Energy of incident photon, $E = hc/ \lambda$
$= (6.626 \times 10^{-34} \times 3 \times 10^8 ) / 589 \times 10^{-9} = 3.33 \times 10^{-19} J/1.6 \times 10^{-19}$
$=2.08 eV$
It can be observed that the energy of the incident radiation is less than the work function of the metal. Hence, no photoelectric emission will take place.
answered Dec 23, 2013 by thanvigandhi_1
edited Apr 2, 2014 by balaji.thirumalai

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