An inspection apparatus for inspecting a flow of particulate material, comprising: a background reflector (105) adjacent which in use falls a flow of particulate material (F); and a lighting unit (107) for illuminating an elongate viewing field (VF) across the background reflector (105), the viewing field (VF) having a first width (w1); wherein the lighting unit (107) comprises a fixed, non-scanning light source (115), and the light source (115) is formed of one or more light elements (120) which define a second width (w2) which is shorter than the first width (w1) of the viewing field (VF).