Finding Work function and Plank constant

[modphysnoob]

Homework Statement

In experiments on lithium, Millikan observed a maximum
kinetic energy of 0.550eV when electrons were ejected with 433.9nm light. When 253.5nm light was
used, he observed a maximum kinetic energy of 2.57eV. Using these results find
a) the work function for lithium, and
b) the predicted value of Planck’s constant.

Homework Equations

h f = work function + kin_max

The Attempt at a Solution

for finding work function

since work function=( h c)/ wavlenght

so we know c , the speed of light , wavelenght, and plank constant so we can find it

however b) ask us to find plank constant , we confuses me

 

[rude man]

1. since work function=( h c)/ wavlenght

Use that formula twice. You're given two sets of max energy and corresponding wavelength. 2 equations, 2 unknowns (work fn and h).

 

[modphysnoob]

Thank you , I just realized that