Energy of photon Example3: The threshold wavelength for a metal surface is 350 nm. What is the ekmax when the wavelength changes to(a)280 nm,(b )380 nm? Solution: hf=E k max tn 0 10=hc/0 hc hc E k max (a)x=280m, EK=1.4×10J=0.89e (b)n=380nm>350nm No ejected electrons 13Energy of photon 13 Example3: The threshold wavelength for a metal surface is 350 nm. What is the Ekmax when the wavelength changes to (a) 280 nm, (b) 380 nm? Solution: max 0 , h k f  E W max 0 k hc hc E      19 max 1.4 10 Ek J  (a)   280nm,   W0 0 0  hf  h c  (b)   380nm  350nm No ejected electrons!  0.89eV