Answer:
6:31 PM
Explanation:
The sun subtends half a degree angle from where we stand. The lower limb of the sun touches the horizon at 6:30 PM.
Now time it takes to disappear completely below the horizon can be calculated as
The Sun diameter is diameter is 32 arc minutes.And its lower limb is 16 arc minutes from the center.
Now, 31 arc minutes = 0.52°
⇒0.52°= 31 arc minutes
therefore, if it crosses its angular diameter sun will set completely
Angular diameter= 0.52°= 31 arc minutes
therefore Sun will set at 6:31 PM