Question

In his explanation of the threshold frequency in the photoelectric effect, Einstein reasoned that the absorbed photon must have the minimum energy required to dislodge an electron from the metal surface. This energy is called the work function () of that metal. What is the longest wavelength of radiation (in nm) that could cause the photoelectric effect in each of the following metals?

(a) Tungsten, = 7.16 10-19 J

__nm

(b) Tantalum, = 6.41 10-19 J

__nm

(c) Silver, = 7.59 10-19

__J

Answer 1

a. E   = hC/

         = hC/E

            = 6.625*10^-34 * 3*10⁸/7.16*10^-19

              = 2.776*10^-17 m   = 2.776*10^-8 nm

b.   E   = hC/

         = hC/E

            = 6.625*10^-34 * 3*10⁸/6.41*10^-19

             = 3.1*10^-17 m

              = 3.1*10^-8 nm

c. E   = hC/

         = hC/E

            = 6.625*10^-34 * 3*10⁸/7.59*10^-19

           = 2.62*10^-17 m

         = 2.62810^-8 nm

(b) Tantalum has longest wave length