Is frictional force and tension the same

Gunpowder residue is most likely to show up where on a shooters hands

Unpolarized light of intensity i_0=750w/m^2 is incident upon two polarizers. after passing through both polarizers the intensity is i_2=280w/m^2. (a) what is the intensity of the light after it passes through the first polarizer in w/m^2? (b) write an equation for the angle between the polarizers in terms of the initial (i_0) and final (i_2) intensities. (c) find the angle between the polarizers in degrees.

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.