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.
The Doppler Effect. In clinical routine, Doppler echocardiography is used used to measure velocities and direction of blood flow in the heart chambers and vessels according to the Doppler effect, which was described by Christian Doppler. He discovered that stars appear of different colours when observed from a constant position on earth.