Question

A star emits light of $5500$ wavelengths. It appears blue to an observer on the earth, which means

Answer 1

Wave's wavelength:

1. The wavelength of a wave is governed by the medium whereby it travels. Waves include sound waves, light waves, water waves, and periodical electrical impulses in a conductor.
2. A sound wave is a fluctuation in air pressure, but light and other electromagnetic waves fluctuate in the strength of the electric and magnetic fields.
3. Water waves are fluctuations in the elevation of a body of water. Atomic positions shift during crystal lattice vibration.
   Blue radiation has a wavelength of roughly $4600$. It demonstrates that the perceived wavelength is less than the true wavelength.

Therefore, it indicates that the star is moving toward the earth.