Mourning doves have a small patch of iridescent feathers. The color is produced by a 330-nm-thick layer of keratin (n = 1.56) with air on both sides that is found around the edge of the feather barbules. For what wavelength or wavelengths in the visible spectrum would this structure produce constructive interference?

Large electric fields in cell membranes cause ions to move through the cell wall. the field strength in a typical membrane is 1.0 x 10 7 n/c. what is the magnitude of the force on a calcium ion with charge +e? what is its acceleration? is it possible for a particle with the same charge as as calcium to have a different acceleration if placed at this location? what would change the acceleration: mass of the particle? diameter of the particle?