Question

The refractive index of glass is 1.5. What will be the speed of light in glass? 1 point 3 X 10⁸ m/sec 1.5 X 10⁸ m/sec 3 X 10⁶ m/sec 2 X 10⁸ m/sec

Answer 1

Answer:

• speed of light in glass = 2 × 10⁸ m/s .

Hence,

Option (d) 2 × 10⁸ m/sec is correct.

Explanation:

Given,

• Refractive index of glass is 1.5

we need to find,

• speed of light in glass = ?

As we know,

• The refractive index of a medium is given by the ratio of speed of light in air and speed of light in given medium.

         n = c / v

[ where n is refractive index of given medium, c is speed of light in air and v is speed of light in given medium ]

→ The speed of light in air = 3 × 10⁸ m/s

so,

Let, speed of light in glass be v

then,

→ refractive index of glass = (speed of light in air) / (speed of light in glass)

→ 1.5 = ( 3 × 10⁸ ) / v

→ v = ( 3 × 10⁸ ) / 1.5

→ v = 2 × 10⁸ m/s

therefore,

• speed of light in glass is 2 × 10⁸ m/s .

Answer 2

Given ,

Refractive index of glass (n) = 1.5

We know that ,

$\boxed{ \sf{Refractive \: index \: of \: medium \: (n) = \frac{Speed \: of \: light \: in \: vacuum}{Speed \: of \: light \: in \: medium } }}$

Thus ,

Speed of light in glass = 3 × 10^(8)/1.5

Speed of light in glass = 2 × 10^(8) m/s

Therefore ,

The speed of light in glass is 2 × 10^(8) m/s