Electromagnetic waves travel at the speed of light, which is approximately 299,792,458 meters per second (about 300,000,000 meters per second or 186,000 miles per second) in a vacuum.
Speed in Different Mediums
- In mediums other than a vacuum, electromagnetic waves travel slower than this speed. This slowdown happens because the electric and magnetic fields of the wave interact with the charged particles in the medium, causing a delay.
- The speed vvv in a medium is related to the speed of light in vacuum ccc by the refractive index nnn of the medium: v=cnv=\frac{c}{n}v=nc.
Summary
- The fundamental speed of electromagnetic waves in vacuum is the universal constant "speed of light" c≈3×108 m/sc\approx 3\times 10^8\text{ m/s}c≈3×108 m/s.
- In materials like air, water, or glass, the speed is slower and depends on the material’s electromagnetic properties.
