Where are magnetic fields strongest near a bar magnet

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative

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.

Give one example to show that when substances are mixed,it may result in a chemical or a physical change depending on the conditions.