Question

uncertainties in millikan's experiment to determine planck's constant

Answer 1

In 1915, Millikan experimentally verified Einstein's all-important photoelectric equation, and made the first direct photoelectric determination of Planck's constant h. Einstein’s 1905 paper proposed the simple description of ‘light quanta,’ or photons, and showed how they explained the photoelectric effect. By assuming that light actually consisted of discrete energy packets, Einstein proposed a linear relationship between the maximum energy of electrons ejected from a surface, and the frequency of the incident light. The slope of the line was Planck’s constant, introduced 5 years earlier by Planck. Millikan was convinced that the equation had to be wrong, because of the vast body of evidence that had already shown that light was a wave. If Einstein was correct, his equation for the photoelectric effect suggested a completely different way to measure Planck's constant.
Millikan undertook a decade-long experimental program to test Einstein's theory by careful measurement of the photoelectric effect, and even devised techniques for scraping clean the metal surfaces inside the vacuum tube needed for an uncontaminated experiment.

“For all his efforts Millikan found what to him were disappointing results: he confirmed Einstein's predictions in every detail, measuring Planck's constant to within 0.5% by his method. But Millikan was not convinced of Einstein's radical interpretation, and as late as 1916 he wrote, ‘Einstein's photoelectric equation cannot in my judgment be looked upon at present as resting upon any sort of a satisfactory theoretical foundation,’ even though ‘it actually represents very accurately the behavior’ of the photoelectric effect. He received the Nobel Prize in part for this discovery nonetheless