Time taken by sunlight to pass through a window of thickness 8 mm and refractive index (3/2) is:

$4×10^{11}s$ $4×10^{-11}s$ $4×10^{-13}s$ $4×10^{13}s$

$4×10^{-11}s$

The correct answer is Option (2) → $4×10^{-11}s$