When sodium metal is illuminated with light of wavelength 4.20 × 102 nm, the stopping potential is found to be 0.65V; when the wavelength is changed to 3.10 × 102 nm, the stopping potential is 1.69V. Using only these data and the values of the speed of light (? = 3 × 108 m/?) and the electronic charge (? = 1.602 × 10−19 C), find the work function of sodium and a value of the Planck’s constant.

When sodium metal is illuminated with light of wavelength 4.20 × 102 nm, the stopping potential is found to be 0.65V; when the wavelength is changed to 3.10 × 102 nm, the stopping potential is 1.69V. Using only these data and the values of the speed of light (? = 3 × 108 m/?) and the electronic charge (? = 1.602 × 10−19 C), find the work function of sodium and a value of the Planck’s constant.