What changes in physical properties can be used as evidence that a chemical reaction occured

Suppose you have three polarizing filters, with the second at an angle of 42∘ to the first and the third at an angle of 90∘ to the first. by what perfect will the original intensity of unpolarized light be reduced to after passing through all three filters?

The slope of a velocity time graph over any interval of time gives the during that interval

Estimate the magnitude of the electric field due to the proton in a hydrogen atom at a distance of 5.29×10 to the power of −11 m, the expected position of the electron in the atom.