When ultraviolet light with a wavelength of 400 nm falls on acertain metal surfa

Question

When ultraviolet light with a wavelength of 400 nm falls on acertain metal surface, the maximum kinetic energy of the emittedphotoelectrons is 1.10 eV. What is the maximum kinetic energyKo of the photoelectrons when light of wavelength 290 nmfalls on the same surface? Use h = 6.63×1034 forPlanck's constant and c = 3.00×108 for the speed of light and express your answer in electronvolts. Use h = 6.63×1034 forPlanck's constant and c = 3.00×108 for the speed of light and express your answer in electronvolts.

Explanation / Answer

wavelength = 400 nm = 400 * 10^-9 m energy E = hc /              = 0.049725* 10^ -17 J               = 4.9725*10^-19 J Maximu kinetic energy K = 1.1 eV = 1.1*1.6 * 10^ -19 J = 1.76* 10^-19 J work function W = E - K = 3.3125*10^-19 J (b). wavelength ' = 290 nm = 290 * 10^-9 m energy E ' = hc / '                 = 6.858 * 10 ^-19 J Maximum kinetic energy K ' = E ' - W                                            = 5.098 * 10^-19 J                                            = ( 5.098*10^-19 ) / ( 1.6 *10^-19 ) eV                                            = 3.18625 eV

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