So, sound is a longitudinal wave, while light is a transverse wave. The speed of sound varies going from one medium to another directly proportional to the bulk modulus and inversely proportional to the density of the new medium (i.e. from air to a steel pipe). Let's say a sound wave (consisting of energy) hit a steel pipe from air, how would the sound transfer (on an atomic level) from the air to the steel pipe and then, finally, travel along the steel pipe for some distance (i.e. 30 feet along the steel pipe from where it transferred to the pipe initially)? Now I know that the bulk modulus (b.m = stress/strain) of the steel pipe is higher than air, meaning that it "stronger" / undergoes less strain, or less deformation with an equal force being present (for both the air and steel). My second question is, why would less deformation to occur in order for the speed of sound to go faster? My thought process is when a sound travels, there will be oscillations that occur in the direction it is traveling. Why less deformation cause sound to better transfer those oscillations (i.e. thinking about the atoms that make up steel)? For light, why would the opposite occur, where n = c/v? Meaning if you go to a denser medium, why would the light wave become slower? In addition, just for clarification, why would energy and frequency stay constant for both types of waves, regardless of the medium?