How did the light theories of Newton and Young/Fresnel explain the transparency of materials such as glass, or opacity of materials such as paper and wood?
Newton's theory of light was largely based on particles or corpuscles, but he did use the aether to explain phenomena such as diffraction. Newton might have thought that materials such as glass let the corpuscles pass through them freely and opaque materials just absorb the corpuscles. Then, there were materials such as metallic surfaces which were opaque but reflective, and it could have been thought that these materials neither let the corpuscles pass through them nor absorb them, they simply reflect them.
In the wave theory of light, the aether was assumed to permeate all material bodies. If it was present in all materials, then why wouldn't all materials be transparent and light could pass through all the materials? Sound waves don't pass through a solid wall because no medium, i.e. air, is present inside the wall.
Could you please help me with it?