obsidian granite reflects light does not reflect light has large visible grains has small invisible grains

Two polarizers are oriented at 40∘ to each other and plane-polarized light is incident on them. if only 16 percent of the light gets through both of them, what was the initial polarization direction of the incident light?

The air that we breath is made mostly of which gaseous molecule

Ascientist wants to test ways to reduce pollution in lake . what is the bestway of doing this