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: A = 3650 , A=4047 , 23=4358 A, 14-5461 , 25= 6907 , The stopping voltages, respectively, were measured to be: Vo1 = 1.28 V, Vo2 = 0.95 V, Vo3= 0.74 V, Vo4 0.16 V, Vos 0V Determine the value of Planck's constant h, the threshold frequency and work function for the material.