  Geometric phase, owing to its topological nature and properties of fault
tolerance, plays an important role in devising real world applications in both
classical and quantum domain. For classical systems, geometric phase has been
observed and studied so far for fully polarized light only. Using an
interferometric experiment we demonstrate, for the first time, the existence of
Pancharatnam-Berry phase for states covering all empty space inside the
Poincar\'e sphere namely the unpolarized and partially polarized light fields.
The observed geometric phase is found identical to its fully polarized
counterpart in excellent agreement with the theoretical predictions.
