question_answer 28)

A mercury lamp is a convenient source for studying frequency dependence of  photoelectric emission, since it gives a number of spectral lines ranging from the UV to the red end of the visible spectrum. In our experiment with rubidium photo-cell, the following lines from a mercury source were used : The stopping voltages, respectively, were measured to be: (a) Determine the value of Planck's constant h. (b) Estimate the threshold frequency and work function for the material.  

Answer:

(a) From the Einstein photoelectric equation, i.e. A graph can be plotted between  and v which comes out to be a straight line Then i.e. (b) Now using we get, or Also,