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.
Spectral lines may also be broadended by: 1  Thermal Doppler Broadening: due to the temperature of the emitter or absorber. 2  Collisional Broadening: due to interactions with neighbouring atoms, ions or molecules. 3  Zeeman Splitting: where energy levels are split into sub-levels by a magnetic field.