Question

Refractive index of glass is 2.0 and that of water is 1.0 if the speed of light in water is 2.5×
{10}^{8}108 
m/s what is the speed of light in a glass. 

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Answer 1

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$\bold{Given:-}$

Refractive index of:-

=> Glass is $2.0$

=> Water is $1.0$

Speed of light in water is $2.5 \times 10^{8} m/s$

$\bold{To\:find:-}$

Speed of light in a glass. 

$\bold{Now,}$

$Refractive \: index \: of \: a \: medium = \frac{c}{v}$

$c = v \times Refr. \: index \: of \: that \: medium$

$2.5 \times 10 ^{8} \times 1.0 = v \times 2.0$

$2.5 \times 10 ^{8} \times 1.0 = v \times 2.0$

$2.5 \times 10 ^{8} = v \times 2.0$

$\frac{2.5 \times 10^{8} }{2.0} = v$

$1.25 \times 10 ^{8} = v$

$\bold{Therefore,}$

$v = 1.25 \times 10 ^{8} m/s$

Speed in the glass is $1.25 \times 10 ^{8} m/s$

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Answer 2

Solutions :-

Given :
Refractive index of glass is 2.0
And refractive index of water = 1.0
Speed of light in water = 2.5 × 10^8 m/s

We know that,
Refractive index of a medium = (speed of light in air)/( speed of light in that medium)
⇒ µ = c/v

According to the question,

⇒ µ = c/v
⇒c = v × µ
⇒ 2.5 × 10^8 × 1.0 = v × 2.0
⇒(2.5 × 10^8)/2.0 = v
⇒1.25 × 10^8 = v

Hence,
The speed of light in a glass = 1.25 × 10^8 m/s