Consider a 6mv photon beam incident on a water phantom at 100cm fsd. the field size on the phantom surface is 10cm x 10cm. draw labelled diagrams showing representative isodose curves for this beam where: a) (3 marks) i) the field edges are symmetric about the central axis. i) an independent jaw has been used to block the beam to the central axis in one dimension. b) explain the differences between the dose distributions observed in part (a).