Question

If the speed of light in glass is $ 2 \times 10^8 \, m/s $ and the speed of light in air is $ 3 \times 10^8 \, m/s $, the refractive index of glass with respect to air is:

• A. 6
• B. 1
• C. 1.5
• D. 5

Hint:

Refractive index \( = \frac{\text{speed of light in vacuum (or air)}}{\text{speed of light in the medium}} \)

Answer 1

The Correct Option is C

Step 1: Recall the definition of refractive index.
The refractive index of a medium (glass) with respect to another medium (air) is the ratio of the speed of light in air to the speed of light in glass: \[ n_{\text{glass, air}} = \frac{\text{speed of light in air}}{\text{speed of light in glass}} \]
Step 2: Identify the given speeds of light.
Speed of light in air, \( v_{air} = 3 \times 10^8 \, m/s \) Speed of light in glass, \( v_{glass} = 2 \times 10^8 \, m/s \)
Step 3: Calculate the refractive index.
\[ n_{\text{glass, air}} = \frac{3 \times 10^8 \, m/s}{2 \times 10^8 \, m/s} = \frac{3}{2} = 1.5 \]