I know there's already a forum for sore and tender scalps but naturally, I can't find it! I needed to register before posting...so it's GONE. For about a year my scalp has been so sore and so tender that it hurts 24 hrs a day. At first I thought perhaps I was allergic to my shampoo so I changed brands. No improvement. Next I wondered if my shower was too hot.
Although small in size, the eye is a very complex organ. The eye is approximately 1 inch (2.54 cm) wide, 1 inch deep and 0.9 inches (2.3 cm) tall. The tough, outermost layer of the eye is called the sclera. It maintains the shape of the eye.
The normal pupil size of a human eye is 4mm, which sets a minimum angular resolution of the eye at [math]2\times10^{-4}[/math]rad. Obviously, we want to put small objects as close to our eyes as possible to be able to see them, but there is a minimum distance for comfortable viewing which is roughly at 25cm. This works out to a size of 0.04mm if the human eye is diffraction-limited, but unfortunately, our eyes do not work at this higher limit.