What is defined as a material resistance to the transmission of light waves flashcards?

This property is called "Opacity".

The question is worded in a difficult way. A more easily understood wording of this question would be:

"What is the name of the property of a material that prevents light passing through?"

For me a person with a phd and who knows what there talking about.i know the chances of a radiation leak is low but if it does the area within a 96.3 mile radius would be unusable because of contamination