In an advanced laboratory class a student performs the photoelectric experiment. Ultraviolet light is shone on a particular metal and the stopping potential is measured at the same time. It is found that 1.99 V is needed to stop all the electrons when the wavelength of the light is 278 nm, and 3.24 V for a wavelength of 230 nm. What is the work function of the metal?
What is Planck's constant based on this measurement?