The Read / Write head of an optical drive consists of a laser emitting diode, a lens, and an optical sensor. The lens focuses the laser beam created by the diode onto the media. The lens is connected with springs that allow small changes to be made to accommodate for small differences in the disc surface. The laser is reflected by the reflective layer, but based on the presence of a Land or Pit (or transparent or opaque area) on the media, the laser is reflected back into the sensor accurately, or is diffused. This difference in intensity of the reflected light is interpreted as binary digits (0s or 1s).