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Surface of certain metal is first illuminated with light of wavelength λ1=350nm and then, by light of wavelength λ2=54nm. It is found that the maximum speed of the photo electrons in the two cases differ by a factor of 2. The work function of the metal (in eV) is close to:
(Energy of photon =1240λ/(innm)eV)
A 1.8
B 1.4
C 2.5
D 5.6