The absolute refractive indices of glass and water are 4/3 and 3/2 respectively. if the speed if light in glass is 2x10^8, calculate the speed of light in
1. vacuum
2. water

2
once check the refractive index of both are they correct?
yes, they are correct.
grammar mistake:- if the speed OF* light

Answers

2015-03-04T00:42:32+05:30

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Refractive index of a medium is defined as the ratio of speed of light in vacuum to speed of light in the medium.

given v_g=2 \times 10^8\ m/s 
Let velocity in vacuum = v
refractive index of glass is 3/2. 
(you have given wrong information.)

\eta_g =  \frac{v}{v_g} \\ \\ \frac{3}{2}=  \frac{v}{2 \times 10^8} \\ \\v= \frac{ 3 \times 2 \times 10^8}{2}= 3 \times 10^8\ m/s

So speed of light in vacuum is 3 \times 10^8\ m/s.

\eta_w= \frac{v}{v_w}\\ \\  \frac{4}{3}= \frac{3 \times 10^8}{v_w}  \\ \\ v_w= \frac{3 \times 3 \times 10^8}{4} =2.25 \times 10^8\ m/s

So speed of light in water is 2.25 \times 10^8\ m/s
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tps i too had got these answer n i wrote them but u deleted it.
yeah...because you had to calculate them. Everyone knows the answer.
ok
2015-03-04T16:57:26+05:30
V=2*10^8m/s
Ng=V/Vg
3/2=3*2*10^8/2
=3*10^8M/S
SPEED OF LIGHT IN VACUM
Nw=V/Vw
4/3=3*10^8/Vw
Vw=3*3*10^8/4
2.25*10^8M/S
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