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Find the threshold wavelengths for photoelectric effect from a copper surface, a sodium surface and a cesium surface. The work functions of these metals are 4.5 e V, 2.3 eV and 1.9 eV respectively. |
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Answer» Solution : If ` lambda_0` be the THRESHOLD wavelength and `varphi` be the work function, ` ( lambda_0)= hc/varphi` `= 1242 eV nm/varphi.` ` For COPPER, lambda_0=(1242 E V nm/ 4.5 e V) = 276 nm. ` ` For sodium, lambda_0= (1242e V nm/ 2.3 e V) = 540nm.` ` For cesium, lambda_0 = (1242 e V nm/ 1.9 e V) = 654 nm.` |
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