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Asked in GUJCET 2023 · Snell's law, slabs and apparent depth
Given: one full turn of 360° in 24 h=86400 s.
Idea: the Sun appears to sweep across the sky at exactly the earth's rotation rate, so angle and time are in direct proportion.
One degree takes (86400)/(360)=240 s, that is 4 minutes.
A minute of arc is 1/(60) of a degree, so it takes (240)/(60).
The Sun shifts by one minute of arc in 4 s.
This is the same arithmetic behind the textbook result that atmospheric refraction, which lifts the Sun by about half a degree, advances sunrise by roughly two minutes.
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