2. Photo-electric effect. when two ultraviolet beams of wavelengths 21 = 80 nm and 12 = 110 nm fall on a lead surface, they produce photoelectrons with maximum energies 11.390 eV and 7.154 eV, respertively. a) Estimate the numerical value of the Planck constant. (b) Calculate the work function, the threshold frequency and the threshold wave-length of lead.

2. Photo-electric effect. when two ultraviolet beams of wavelengths 21 = 80 nm and 12 = 110 nm fall on a lead surface, they produce photoelectrons with maximum energies 11.390 eV and 7.154 eV, respertively. a) Estimate the numerical value of the Planck constant. (b) Calculate the work function, the threshold frequency and the threshold wave-length of lead.