Find σ12 so that the stress distribution is in equilibrium with zero body force and so that the traction vector on the plane x1 = 1 is given by t = (1 + x2)e1 + (5 − x2)e2.

In order of decreasing light-transmitting capabilities of materials, which is the correct sequence? a. transparent -> translucent -> opaque b. opaque -> transparent -> translucent c. opaque -> translucent -> transparent d. translucent -> transparent -> opaque