Light with orbital angular momentum will undergo a frequency shift when it bounces of a rotating object.
There are diffraction patterns that form when laser light shines on a feather. Researchers have compared the patterns with the expected pattern using measurements of the bard spacing obtained from electron microscope data.
This novelty item is composed of two layers of cardboard with a small hole, about 6 mm in diameter, punched through both layers. A feather is embedded between the layers of each lens. Because the vanes of the feather are so close light is diffracted, causing the user to recieve two slightly offset images. You can think about how this would work if you were viewing a pencil; where there are two offset images of the pencil a darker image is obtained giving the illusion that one is seeing the graphite embedded with the body of the pencil.
The incoming radiation is split into two beams, which are reflected off mirrors so that they come back to the same location and interfere with each other. (Make your own Michelson stellar interferometer shown here.)
An object's angular size is the angle between the lines of sight to its two opposite sides. For example, the angular size of the horizon is about 180 degrees. An object's angular size is a measure of how large the object actually appears to be (which is a function of both actual size and distance away).
Fraunhofer lines are typical spectal absorption lines. In the Sun, Fraunhofer lines are seen from gas in the outer regions of the Sun, which are too cold to directly produce emission lines of the elements they represent.
A wineglass produces results similar to those seen in galaxies that are affected by gravitational lensing. An "Einstein ring" is seen when looking right down the wineglass stem through the bowl of the glass, with the candle flame sitting right in the center.
