It is known that ZnWO4, (Eg approx 3.6-3.8 eV), owing to direct band gap should show negligible photocatalytic activity the in visible range and only in UV range. On the other hand, beta ZnMoO4 (Eg approx 3.2-3.4), with indirect band gap shows photocatalytic activity in visible range. Upon substitution of Molybdenum in ZnWO4, the mixed solid solution should ideally show better efficiency in Visible range. But how do we conclude that the mixed solid solution of ZnW(1-x)Mo(x)O4 will show better photocatalysis in which system (UV or visible)? What should be the ideal experimental apparatus?