Given, transition levels, n1=2,n2=3 Energy emítted during transition n2=3 to n1=2 in H-atom (i.e. for Hα - light) E=13.6[
1
n12
−
1
n22
]=13.6[
1
22
−
1
32
] =13.6[
5
36
]eV=1.89eV For Hα-light to be able to emit photoelectrons from a metal, the work function must be less than or equal to 1.89eV. Hence, maximum value of work function =1.89eV