@[email protected] of radiation in a generally backward direction. In the @[email protected] of @[email protected], it applies to the @[email protected] of radiation into the @[email protected] from any material except the sample and the detector. In @[email protected], it is said to occur when the @[email protected], \(\theta \), is \(180^{\,\unicode{x26ac}}\). Conversely, forward scattering occurs when \(\theta \) is \(0^{\,\unicode{x26ac}}\).