Practice portal › Ray Optics and Optical Instruments › Refraction and Total Internal Reflection
Asked in GUJCET 2020 · Snell's law, slabs and apparent depth
Given: one full turn of 360° takes 24 hours.
Idea: the sun's apparent march across the sky is just the earth's rotation seen from the ground, so angle and time are in direct proportion.
Rate =(360°)/(24 h)=15° per hour.
Time for 1°=(60 min)/(15)=4 min.
This is the arithmetic behind the roughly two-minute early sunrise and late sunset caused by atmospheric refraction: the bending lifts the sun by about half a degree, and half a degree is worth about two minutes.
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