A multi-well plate reader including an emitter assembly having a plurality of emitters and a receptor assembly including a plurality of receptors separated by at least one spacer element such that a multi-well plate can be inserted between the emitter assembly and the receptor assembly. The emitters and receptors are paired and arranged in parallel arrays such that electromagnetic radiation can be transmitted through each well of the multi-well plate to a corresponding receptor to determine the opacity of the biological material contained within the well. Each well of the multi-well plate can be evaluated by a different emitter receptor pair allowing the entire multi-well plate to be efficiently monitored at a high throughput.