Speed of light in vacuum is _______ m/s 

The correct answer is 2)3 × 108.

Key Points

• The speed of light in vacuum is approximately 3 × 10⁸ meters per second (m/s).
• This value is universally recognized and is denoted by the letter c in physics equations.
• It is a fundamental constant in physics, used in the theory of relativity and various other scientific calculations.
• The exact value is 299,792,458 meters per second.
• This speed is the maximum speed at which all energy, matter, and information in the universe can travel.

Additional Information

• Electromagnetic Spectrum:
  • The speed of light in vacuum applies to all electromagnetic waves, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
  • These waves travel at the same speed in a vacuum but have different wavelengths and frequencies.
• Relativity:
  • Albert Einstein's theory of relativity relies heavily on the constant speed of light.
  • In the equation E=mc², c represents the speed of light, linking energy (E) and mass (m).
• Refractive Index:
  • The speed of light changes when it passes through different mediums such as air, water, or glass.
  • The ratio of the speed of light in a vacuum to its speed in a given medium is called the refractive index of that medium.
• Measurement:
  • The speed of light was first measured by Ole Rømer in 1676, using observations of Jupiter's moons.
  • Modern methods involve laser interferometry and atomic clocks for high precision.