There is a previous thread:- https://www.physicsforums.com/archive/index.php/t-208429.html
. After viewing it, you will be able to understand the meaning of cutoff potential more clearly. It is used to calculate the work function and not the kinetic energy.
You are right in saying that the volume calculated by you would be larger and also more accurate. But the point I tried to make was that although it would be larger, but it would not be significantly larger (in fact very small relative to the rest of the terms). Therefore, it is simpler and less...
Max K.E. = h(v-vo) = hv - Work function
where h is Planck's constant, v is frequency of radiation and vo is the cutoff frequency. As you have already calculated the work function, therefore you can create the graph (which will be a straight line).
According to the photoelectric equation,
Energy of light radiation = Kinetic Energy of photoelectron + Work function
Here, you are actually calculating the work function and thinking that it is the Kinetic Energy. Calculate the energy of the light radiation [hc/(wavelength)], where h is...
The approach is quite correct. But if you are aware of the fact that the coefficient of volume expansion (i.e. beta) is equal to 3*(alpha), then you might have used a simpler method. You could have used the equations:-
(V-final)=(V-initial)[1 + (beta)(delta-T)]
(beta)=3*(alpha)
For water...