Sound waves travel faster in diamonds than in air due to the difference in the materials' physical properties. The speed of sound in a medium is determined by the density and the elastic properties of the material.
Diamonds have a much higher density and a higher elastic modulus (measure of stiffness) compared to air. The densely packed carbon atoms in a diamond lattice result in a high density of the material. This high density causes sound waves to propagate more quickly through the diamond compared to the sparse molecules in air.
Moreover, diamonds have a high elastic modulus, which means they are very stiff and resist deformation when subjected to an applied force. This stiffness allows sound waves to travel through the diamond with less resistance and faster propagation.
In contrast, air has a low density and a lower elastic modulus compared to diamonds. The low density of air molecules means there are fewer particles available to transmit and carry sound energy, resulting in slower sound propagation. Additionally, the lower elastic modulus of air allows it to be easily compressed and expanded, which leads to slower sound wave transmission.
Therefore, due to the higher density and higher elastic modulus of diamonds compared to air, sound waves can travel faster in diamonds than in air.