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?

magnified images possible images can be real = projected onto a screen

no

sodium is solid at rt

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia