In the evening you go back to the swimming pool with your friends. The object is still lying on the bottom of the pool in the same location as before, but since it's dark now, you use a flashlight to show it to your friends. Remembering the apparent location of the object in daylight, where should you aim to illuminate the object with the flashlight? Assume you hold the flashlight at eye level.

Asheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200oc and is permitted to achieve a steady-state diffusion condition. the diffusion coefficient for nitrogen in steel at this temperature is 6 x 10- 11 m2 /s, and the diffusion flux is found to be 1.2 x 10-7 kg/m2 -s. also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m3 . how far into the sheet from this high-pressure side will the concentration be 2.0 kg/m3 ? assume a linear concentration profile.