Section through crystal on plane of images: assumed geometry
The angle λ between the tensile axis and the slip direction cannot be measured directly from these images. However, an estimate of λ can be made by assuming that the slip plane normal and the slip direction are coplanar, and that these vectors both lie in the plane of the image. In this case, λ = 90° - φ. Check to see if l sin λ is constant for the two deformed samples.