Q. A short brass cylinder of diameter D = 10 cm and height H = 12 cm is initially at a uniform temperature Ti = 120oC. The cylinder is now placed in atmospheric air at 25oC, where heat transfer takes place by convection, with a heat transfer coefficient of h = 60 W/m2.K. Calculate the temperature at the center of the cylinder 15 min after the start of the cooling.
Q. The resolution of the eye is ultimately limited by pupil diameter. What is the smallest diameter spot the eye can produce on the retina if the pupil diameter is 4.45 ? Assume light with a wavelength of = 600 . (Note: The distance from the pupil to the retina is 25.4 . In addition, the space between the pupil and the retina is filled with a fluid whose index of refraction is = 1.336.)