The first excited state of sodium decays to the ground state by emitting a photon of wavelength 590 nm. If sodium vapor is used for the Franck-Hertz experiment, at what voltage will the fourth current drop be recorded

The voltage would be        

Explanation:

From the question we are told that

        The wavelength is

 Generally when a electron changes state to a higher state  an energy(E)  is given off and this  is equivalent to eV

So  the  voltage  of the electron can be evaluated as

Where h is the planks constant with a constant value  

            c is the speed of light  

             e is the value charge in one electron

      Substituting value

So the fourth current drop would be recorded when electron has change state four times and the voltage at this point can be mathematically evaluated as

b.a device that inputs heat into a cool object