Question

What is the speed of light in free space?

• A. 3.5 ×10⁸ m/s
• B. 3 ×10⁸ m/s
• C. 3 ×10⁹ m/s
• D. 3.5 ×10⁹ m/s

Answer 1

Answer:

B. 3 ×10⁸ m/s

Speed of light:

• The speed of light is dependent on the refractive index of the medium it is travelling in.

• The higher the refractive index of the medium, the lower is the speed of light.

• Hence, the speed of light in a medium is inversely proportional to the refractive index of the medium in which it is travelling through.

• The denser a medium, the more is its refractive index and thus, the lesser is the speed of light.

• The speed of light is thus minimum in solids as they are denser and will be maximum in a vacuum as a vacuum is the least dense medium.

• Speed of light in free space / air is 3 ×10⁸ m/s