Question

At what speed do all electromagnetic waves travel in a vacuum?

Options

• A speed that increases from radio waves to gamma rays

• \[3 \times 10^{8}\,\mathrm{km/s}\]

• \[3 \times 10^{6}\,\mathrm{m/s}\]

• \[3 \times 10^{8}\,\mathrm{m/s}\]

Answer 1

All electromagnetic waves have the same speed in a vacuum: \[3 \times 10^{8}\,\mathrm{m/s}\]. Their frequencies and wavelengths differ, but their vacuum speed does not.