Projection apparatus and method for switching operation modes thereof

A projection apparatus includes a light source module, a first color wheel, a second color wheel and a control unit. The light source module provides an illuminating light beam. The first and the second color wheels are disposed on an optical path of the illuminating light beam. The first and the second color wheels respectively have a first white segment and a second white segment with unequal areas. The control unit is electrically coupled to the first and the second color wheels. In a first mode, the control unit controls the first white segment to stop on the optical path and controls the second color wheel to rotate. In a second mode, the control unit controls the second white segment to stop on the optical path and controls the first color wheel to rotate.