Because it determines if it is isolated or not. This means if other substances can enter or not. This usually relies on the membrane with it´s pores. The pores help the membrane be selectively permeable in what it lets in and out.
Just divid the distance by time
It serves to polarization by transmission through a filter. <span>A Polaroid filter is a device used to polarize light. The device filters out one-half of the vibrations of unpolarized light as the light passes through the filter. Unpolarized light enters the Polaroid filter and the polarized light goes out from the filter. The unpolarized light becomes polarized.</span>
