JAMB - Physics (2007 - No. 18)
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 10\(^8\) ms-1]
[c = 3.0 x 10\(^8\) ms-1]
4.5 x 10-11s
4.5 x 10-10s
4 .5 x 10-12 s
3.0 x 10-10s
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 = \( \frac{9 x 10^{-3}}{2.0 x 10^8}\)
∴ Time = 4.5 x 10\(^{-11}\)S
(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 = \( \frac{9 x 10^{-3}}{2.0 x 10^8}\)
∴ Time = 4.5 x 10\(^{-11}\)S
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