1 Many people find that boxes with a 1.25 or 1 1/8 hole restrictor on them before an egg is laid are not utilized, even by smaller birds like titmice and chickadees. 2  If the entrance hole is enlarged (e.g., by woodpeckers or chewing rodents), put a hole reducer on it.
The Doppler effect widens the spectral lines of rotating objects because the wavelengths changes from blue or red. Blue-shifted, red-shifted, and non-shifted photons mix together to get how its rotating.
when the speed of source is greater than the speed of the wave then the doppler effect... light emission caused by atoms which are excited by an outside source. light emission caused by atoms which are excited by an outside source. the emission of electrons by a substance when illuminated by electromagnetic radiation..