Crystals tend to exhibit the hcp structure alone ( random stacking of hexagonally close-packed crystal planes ), in contrast with a mixture of ( rhcp ) and face-centred cubic packing when allowed sufficient time to reach mechanical equilibrium under gravitational forces on Earth.
22.
If the sample is oriented so that one particular plane is only slightly tilted away from the strongest diffracting angle ( known as the Bragg Angle ), any distortion of the crystal plane that locally tilts the plane to the Bragg angle will produce particularly strong contrast variations.
23.
The most common principle used is interference in the form of zone plates, refraction in compound refractive lenses that use many small X-ray lenses in series to compensate by their number for the minute index of refraction, Bragg reflection off of a crystal plane in flat or bent crystals.
24.
In this version, the outlined black box that enclosed the three rings and the vertical line ( that maintained their 1996 design ) was replaced by a grey square ( a crystal plane when rendered in 3D ) and the ABS and CBN names joined together to form ABS-CBN's name, now situated below the symbol.
