Question

a glass plate 0.9m thick has a refractive index of 1.5.how long does it take a pulse of light to pass through it

Answer 1

speed = 3 * 10^8 m/s / 1.5 = 2*10^8 m/s
distance = 0.9 meters (really ? )

time = (0.9 /2) * 10^-8 seconds