A glass plate 0.9cm thick has a reflective index of 1.50. how long does it take for a pulse of light to pass through the plate?
[c = 3.0 x 8 ms-1]
[c = 3.0 x 8 ms-1]
-
A.
4.5 x 10-11s -
B.
4.5 x 10-10s -
C.
4 .5 x 10-12 s -
D.
3.0 x 10-10s
Correct Answer: Option C
Explanation
N = 1.5 = (speed of light in glass)/speed of light in air
(1.5)/1 = (3.0 x 108)/V
V = (3.0 x 108)/1.5
V = 2.0 x 108 ms-1
But x = Vt
t = (x)/Vt
t = (x)/v = (9 x 10)4/2.0x 108 = 4.5 x 10-2S
∴ Time = 4.5 x 10-12S