You’ve been promoted to the acoustics company! You’ve moved from the shipping department to research and development. Your first client presents you with a problem. They moved into a new condo, but the upstairs neighbours make a lot of noise. The client has tried earplugs, noise-cancelling headphones, and white noise, and yet nothing has worked. They can still hear every step their neighbours take. You recommend installing sound-absorbing material in the client's ceiling so that the neighbours’ sounds will no longer be heard. Describe the properties and structure of the material you recommend. Then explain in terms of energy and the material’s structure how it will physically absorb the sound. Maxium of 800 characters including spaces.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.

maria has a savings account that is earning simple interest. if she started with $200 in the account and has earned a total of $8 in interest in two years, what is the rate of the account? use the formula  .