Given an unknown mixture consisting of two substances, a scientist can determine whether a specific mixture is a true solution, a colloid, or a suspension by passing a light through the mixture. They are distinguished by the Tyndall Effect. If the mixture is a solution, light just pass through the mixture. The light does not reflect. If the mixture is a colloid, then light is dispersed or reflected due to the colloidal particles. If the mixture is a suspension, light cannot pass through.