Question

refractive index of Glass is 1.65 what is the speed of light in the glass​

Answer 1

Given :

$\bf Refractive \: index \: of \: flint \: glass, \: η_{g} = 1.65$

To Find :

$\bf Speed \: of \: light \: in \: glass, v_{g}$

Solution :

$\bf We \: know \: that \: speed \: of \: light \: in \: air, c=3×10⁸m/s$

Now, by formula :

$\bf η_{g} = \dfrac{c}{v_{g}}$

$\bf \implies v_{g} = \dfrac{c}{η_{g}}$

$\bf \implies v_{g} = \dfrac{3 \times 10^{8}m/s}{1.65}$

$\bf \implies v_{g} = \dfrac{3}{1.65}\times 10^{8}m/s$

$\bf \implies v_{g} = \dfrac{3 \times 100}{165}\times 10^{8}m/s$

$\bf \implies v_{g} = \dfrac{\cancel{3} \times 100}{\times{\cancel{165}}_{55}}\times 10^{8}m/s$

$\bf \implies v_{g} = \dfrac{100}{55}\times 10^{8}m/s$

$\bf \implies v_{g} = 1.8181... \times 10^{8}m/s$

$\bf \implies v_{g} = 1.82 \times 10^{8}m/s \: (approx.)$

$\bf \therefore Speed \: of \: light \: in \: glass, v_{g} = 1.82 \times 10^{8}m/s \: (approx.)$

Answer 2

Answer: 1.8182×10⁸ m/s

Explanation: Given : Refractive index of Glass is 1.65

To Find : what is the speed of light in the glass​

Solution : We know that refractive index of light is defined by η=

speed of light that medium/speed of light in vaccum

​η= v

3×10 /8

 =1.5

v=2×10 /8 m/s

1.8182×10⁸ m/s

The refractive index of glass for visible light is normally about 1.5, implying that light in glass travels at c1.5 200000 km/s (124000 mi/s); the refractive index of air for visible light is around 1.0003, implying that light in air travels at roughly 90 km/s (56 mi/s) slower than c .

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