When UV light at 584 nm from a helium lamp is directed up on

When UV light at 58.4 nm from a helium lamp is directed up on a sample of krypton,electrons are ejected with a speed of 1.79×106 m/s. Calculate the ionization potential of krypton.

Solution

Calculate the energy of the UV photon using planck\'s law.

E = hf=hc/(lambda) =6.626 *10^-34 /58.4*10^9=1.13*10^-44

Then subtract off the kinetic energy of that electron. It\'s not relativistic, so 1/2 mv^2 will work fine.

=1/2*9.1*10^-31*(1.79×10^6)^2

=1.45*10^-18