Frequency Comparison

[Christine Chen 1H]

Can somebody explain why in graph 1.17 of edition 6, Na has a greater frequency of radiation (v) than K and Rb? What properties of an element cause the frequency to be higher?

[klarratt2]

The frequency of radiation is different for each metal because they each have different work functions. When each line intercepts the x axis corresponds to the threshold energy of that metal (where the energy to remove an electron from that metal equals the energy of the incoming photon, making the kinetic energy equal zero). Since each metal has a different work function, each will take a different amount of energy to remove an electron. E=hv, so different energies means different v. Na has a greater frequency of incident radiation because it takes more energy to remove one electron from it.