After deformation by 40% to l1 = 25 mm, slip steps have appeared on the surface of the crystal. From this micrograph, it is possible to measure an approximate value for φ1, the angle between the slip plane normal and the tensile axis. The image has been taken with the 'narrow edge' of the deformed specimen perpendicular to the electron beam. Try to estimate φ1 from the picture, assuming that the tensile axis and the slip plane normal both lie in the plane of the image. The answer is given on the next page.