Which of e following conditions would decrease the ability of a person to bear a sound?

a. the frequency of the sound remains steady at 100hz.
b. the liquid medium in which the sound travels is replaced with elastic solid.
c. a wave loses energy as it moves through a medium.
d. the distance to the sound source becomes shorter.

Amichelson interferometer operating at a 600 nm wavelength has a 3.02-cm-long glass cell in one arm. to begin, the air is pumped out of the cell and mirror m2 is adjusted to produce a bright spot at the center of the interference pattern. then a valve is opened and air is slowly admitted into the cell. the index of refraction of air at 1.00 atm pressure is 1.00028.how many bright-dark-bright fringe shifts are observed as the cell fills with air?