There is a membrane made of an isotropic material whose elastic modulus and poisson’s ratio are e and ν, respectively. when this membrane is elongated along x-direction with no lateral deformation in y-direction, the apparent elastic modulus (e’) determined by measured values of stress and strain in x-direction (σx and εx) should be greater than the material’s own modulus (e) due to poisson’s effect. determine the difference between e’ and e.