Two small rings each of weight w can slide on a fixed rough horizontal rod. the rings are attached one to each end of a uniform chain of weight 4w and length 4a so that the chain hangs freely from the rings. if the coefficient of friction between each ring and the rod is 1/2, find the distance between the rings when they are in limiting equilibrium. prove that the lowest point of the chain is then at a depth a below the rod.

Antireflective coatings on solar cells are often made by applying a thin film of silicon nitride (sinx), which has an index of refractive of 1.2, on the top of the silicon solar cell, which has a refractive index of about 3.5. however, the sun emits radiation of various wavelengths which the solar cell absorbs, and the antireflective coating can only absolutely minimize the reflection of one of these wavelengths. the coating thickness is chosen to reduce the reflection of green/yellow light (e = 2.2 ev), which is the most intense color in the solar spectrum (shown below). which of the following coatings would minimize reflection of green/yellow light? the answer is 820 nm how? what is the angular width of the central maximum of an electron traveling at 2 x 108 m/s going through a single slit of width 1 mm.