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The work functions `(W_(0))` of K, Na, Li, Mg and Cu are 2.25,2.30,2.42,3.70 and 4.80 eV respectively. How many of these metals do not undergo photoelectric effect when a radiation of wavelength 450 nm is allowed to fall on them? `(1eV=1.602xx10^(-19)J)`A. 2B. 1C. 3D. 5 |
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Answer» Correct Answer - A Ejection of photoelectron takes place when the absorbed quantum energy exceeds threshold energy. `E_("absorbed")=(hc)/(lamda)` `=(6.626xx10^(-34)xx3xx10^(8))/(450xx10^(-19))` `=4.417xx10^(-19)J` `(4.417xx10^(-19))/(1.602xx10^(-19))eV` =2.75eV Thus, Mg and Cu i.e., two metals will not eject photoelectron from the given radiation. |
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