What material causes a wave to bounce off of it

Its a Reflector

Reflector is some sort of material that is used to collect or bounce off energy such as sound, light, or radio wave

Usually it took form in some sort of parabolic that revolve around an axis

Interference.
hope that this helps you! =)

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf   

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