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Earlier discussion
2 older comments kept for context.
CHISOM EUSTACE
n=Vair/Vglass.......(1)
n=1.5,Vlight=3×10⁸m/s
Substituting in eqn..(1)
1.5=3×10⁸/Vglass
Vglass=3×10⁸/1.5
Vglass=2×10⁸m/s
Then thickness of glass is equivalent to the distance of the glass in which the speed of light must cover which is equal to 0.9cm. Equivalent to 0.009m because the speed of light in glass is in metres.
Having;
Vglass=2×10^⁸
Thickness=Dglass=0.009m
time,t=?
V=d/t becomes; Vglass=Dglass/Time
2×10⁸=0.009/Time
Time=0.009/2×10⁸ or Time= 0.009/200000000
Time=4.5×10^-11 or 0.000000000045.
Oluwaseun Adeyemi
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