A 30 year old female complains of spacing between her upper front teeth. Intra-oral examination reveals a 2 mm diastema present between the upper central incisors. Direct composite restoration is done to close the diastema. The restorative material used in this patient must have:
The absorption coefficient is the fraction of incident light flux lost by absorption in an elementary layer. The absorption coefficient, K, for a unit thickness of a material is defined as follows:
	 K = S(a − 1) mm−1
Composites with larger values of the absorption coefficient are more opaque and more intensely colored.
The scattering coefficient is the fraction of incident light flux lost by reversal of direction in an elementary layer. Composites with larger values of the scattering coefficient are more opaque.
Sufficient radiopacity is required in an x-ray image in order to assess restorations for marginal defects or breakdown, help differentiate composite restorations from dental caries, and detect microleakage. 

Craig’s Restorative dental materials. 14th edition page Pg-54
Low absorption coefficient
Low scattering coefficient
Radiopacity
All of the above