Wave Propagation In Vacuum

As emphasised in NCERT Class 12, Chapter 8 (Electromagnetic Waves), an electromagnetic wave is generated by mutually inducing electric and magnetic fields: a changing electric field creates a magnetic field through the Ampere-Maxwell law, and a changing magnetic field creates an electric field through Faraday's law. This self-sustaining regeneration, in which each field continuously produces the other, allows the wave to propagate through empty space without any material medium. Sound, by contrast, is a mechanical wave that needs particles of a medium to vibrate and pass the disturbance along, so it cannot cross the vacuum between the Sun and Earth. This is precisely why we see sunlight but hear no sound from the Sun. The claim that electromagnetic waves need a denser medium is the opposite of the truth, since they travel fastest in vacuum. The idea that sound overshoots the Earth is meaningless because sound simply cannot travel through vacuum at all. The statement that electromagnetic waves are longitudinal and sound is transverse reverses reality: electromagnetic waves are transverse and sound in air is longitudinal. A conceptual check confirms that the defining property enabling space travel is the medium-independent, self-regenerating field structure of electromagnetic waves.