(i) Sound waves are mechanical waves which are longitudinal in nature. Light waves are electromagnetic waves which are transverse in character.
(ii) Sound waves need a material medium for propagation, whereas light waves do not need any medium.
(iii) Velocity of sound waves in air at 0°C » 332 m/s,
whereas velocity of light waves in air/vacuum 3 x ${{10}^{8}}$ m/s.