Twinkling of Stars
- The twinkling of stars is also due to atmospheric refraction.
- The air in the earth's atmosphere is such that it has increasing refractive index
- When starlight enters earth's atmosphere it undergoes multiple refraction continuously before it reaches the earth
- Because of the increasing refractive index, the starlight bends downwards (ie towards the normal) and thereby the apparent position of the star is slightly higher than its actual position.
- Also, this apparent position of the star is not fixed. It keeps on changing slightly since the atmospheric conditions of the earth keep varying
- But however the stars are so distant that they appear fixed to the naked eye
Early sunset and Delayed sunrise
- Atmospheric Refraction is the same reason that the sun is seen about 2 minutes before actual sunrise and is seen for about 2 minutes after sunset.
- The actual position of the sun is slightly shifted from the actual position of the sun