need help!! In the first law of thermodynamics, ΔE=Q−W , what does Q stand for? the work done by the piston the heat added to the system the change in the internal energy of the system the internal energy of the system

Light from two different sources are incident upon the same side of a polarizing filter. light from one source is polarized with total intensity ip, while light from the other source is unpolarized with total intensity iu. as you rotate the polarizing filter through 360 degrees, the intensity of the transmitted light on the other side varies by a factor of 9. what is the relative intensity of the initial polarized source to the unpolarized source, or ip/iu?