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.
Source(s): Theories: 1.Doppler Effect: light that is emitted by something moving away from us appear more red, and light emitted by something moving towards us appear more blue. 2.The brightness and color of a star depend on its surface temperature, which in turn depends on its mass.tars emit colors of many different wavelengths, but the wavelength of light where a star's emission is concentrated is related to the star's temperature-the hotter the star, the more blue it is; the cooler the star, the more red it is.