What wavelength of light is shining on a metal with work function ?=2.8??, if the stopping potential for the photocurrent (ejected electrons) is 5??

In a photoelectric experiment using a sodium surface, you find a stopping potential of 1.86 V for a wavelength of 300 nm and a stopping potential of 0.885 V for a wavelength of 393 nm. From these data find (a) a value for the Planck constant, (b) the work function for sodium, and (c) the cutoff wavelength Ao for sodium. (a) Number i (b) Number i (c) Number i Units Units Units >

Light of constant intensity but varying wavelength was used to illuminate the cathode in a photoelectriceffect experiment. The graph shows how the stopping potential depended on the frequency of the light. What is the work function, in eV, of the cathode?

When ultraviolet light with a wavelength of 351 nm falls on a certain metal surface, the maximum kinetic energy of the emitted photoelectrons is measured to be 1.76x10-19 J. How much energy, in Joule, does an electron have to gain in order to escape from the metal surface? Exponential format with 3 SF.