The speed of electromagnetic waves in vacuum is approximately what value?

The speed of electromagnetic waves in vacuum is approximately what value?

• A. 3.00 x 10^6 m/s
• B. 3.00 x 10^8 m/s
• C. 3.00 x 10^5 m/s
• D. 3.00 x 10^10 m/s

Answer: (B)

In vacuum, all electromagnetic waves travel at the same speed, called c, which is about 3.00 × 10^8 meters per second. This constant comes from the properties of empty space and is related to Maxwell’s equations through c = 1/√(μ0 ε0). That means regardless of whether you’re dealing with radio waves, visible light, or X‑rays, their speed in vacuum remains essentially the same. In media other than vacuum, the speed slows down by the medium’s refractive index, v = c/n, but in vacuum it sits right around 3.00 × 10^8 m/s. The other numbers are not speeds in vacuum: they would correspond to much slower speeds in materials or even exceed the universal speed limit if used as a vacuum value.

In vacuum, all electromagnetic waves travel at the same speed, called c, which is about 3.00 × 10^8 meters per second. This constant comes from the properties of empty space and is related to Maxwell’s equations through c = 1/√(μ0 ε0). That means regardless of whether you’re dealing with radio waves, visible light, or X‑rays, their speed in vacuum remains essentially the same. In media other than vacuum, the speed slows down by the medium’s refractive index, v = c/n, but in vacuum it sits right around 3.00 × 10^8 m/s. The other numbers are not speeds in vacuum: they would correspond to much slower speeds in materials or even exceed the universal speed limit if used as a vacuum value.