A mercury lamp is a convenient source for studying frequency dependence of photo electric emission , Since it gives a number of spectral lines rating 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 where used . λ1=3650A∘,λ2=4047A∘,λ1=4358A∘,λ4=5461A∘,λ5=6907A∘The stopping voltages respectively were measured to be : Vo1=1.28v,Vo2=0.95v,Vo3=0.74v,Vo4=0.16v,Vo5=1.28v Determine the value of plark's constant be