SUBSTANCE

SPEED OF LIGHT

DENSITY ρ

AIR

3 × 10⁸ m/s

1.225 kg/m³

WATER

2.25 × 10⁸ m/s

1000 kg/m³

GLASS

2 × 10⁸ m/s

2500 kg/m³

DIAMOND

1.25 × 10⁸ m/s

3500 kg/m³