If Cu2+ ions and Fe3+ ions are both suspected of being present in the solution, will Fe3+ ions interfere with the analysis of Cu2+ at the wavelength selected? Why or why not?

No, Fe^3+will not interfere

Explanation:

Whether of not the two ions will interfere will depend on the region of the visible spectrum where they absorb.

Now Fe^3+  at a wavelength of 600nm for the determination of Cu^2+ ion will not interfere.  This is because,  Fe^3+ absorbs in the blue (450-480 nm) region while Cu+2 absorbs in the yellow (560-600 nm) region then appears blue in color.