Look at the photo below

Advanced Sunrise - Example.jpg

Here, we see sun above the horizon, but the sun is actually not above the horizon.

 

Infact:

We see sunrise 2 minutes before actual sunrise

We see sunset 2 minutes after sunset

This is because of atmospheric refraction

 

Explanation for Advanced Sunrise

Before Sunrise, sun is below the horizon

Sun's rays are coming from more dense air towards less dense air

This causes sun rays to refract and appear to come above the horizon

Our eyes see sun rays as a straight line, it appears to us that sun has risen but it has actually not yet risen

Explanation for Delayed Sunset

After Sunset, Sun is below the horizon

Sun's rays are coming from more dense air towards less dense air

This causes sun rays to refract and appear to come above the horizon

Our eyes see sun rays as a straight line, it appears to us that sun has not yet set

reason-of-advanced-sunrise-and-delayed-sunset---teachoo.jpg

What about Flattening of Sun's Disc?

During sunrise and sun's set, shape of sun appears to be little flatter

This is also because of refraction of light (bending of light coming from sun to earth due to earth's atmosphere)

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Maninder Singh's photo - Co-founder, Teachoo

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo