Question

If the speed of light in a medium is 1 x 10⁸ m/s. What is the refractive index of the medium ?

• A. 3
• B. 5
• C. 20
• D. 10

Answer 1

Answer:

A. 3

• Refractive Index Definition: The refractive index (n) of a medium is defined as the ratio of the speed of light in a vacuum (c) to the speed of light in that specific medium (v).

• Formula: The mathematical representation is n = c / v.

• Constants: The speed of light in a vacuum (c) is approximately 3 × 10 x8 m/s.

• Calculation Steps:

  • Given v = 1 × 10⁸ m/s.

  • Substituting the values: n = (3 × 10⁸) / (1 × 10⁸).

  • Result: n = 3.

  • Refractive index is a dimensionless quantity because it is the ratio of two similar physical quantities (speeds).

  • It provides information about how much the light is refracted (bent) when entering the medium.

  • The refractive index of a vacuum is exactly 1, which is the lowest possible value.

  • For air, the refractive index is approximately 1.0003, often approximated to 1 in competitive exam problems.

  • Materials with higher refractive indices are considered optically denser.