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.
One example of Doppler effect is when you hear an ambulance go by, and the pitch of the siren goes up as it get closer, and goes down after it passes you by. Another exampleâ¦ of Doppler effect is red shift, where the color of distant stars seem to shift towards the red end of the spectrum, because the stars are receding from us.