The redox half-reaction of potassium dichromate (K2Cr2O7) can be determined by considering the changes in oxidation states of the elements involved.

In the case of potassium dichromate, the chromium atom undergoes a change in oxidation state from +6 to +3. This reduction half-reaction can be represented as follows:

Cr2O7^2- + 14H+ + 6e- -> 2Cr^3+ + 7H2O

In this reaction, the dichromate ion (Cr2O7^2-) is reduced to chromium ions (Cr^3+), and water molecules (H2O) are formed.

It's important to note that this represents only the reduction half-reaction. The corresponding oxidation half-reaction would involve another species losing electrons to balance the overall redox reaction.