If you were trying to build a soundproof room, which of the following materials would you choose in order to absorb the most sound, based on the coefficient of absorption for each material?
a. wood
b. concrete
c. heavy curtains
d. carpet
i'm thinking wood to absorb sound but i'm also thinking concrete to block it. but wouldn't that make it echo?

Coefficients of Absorption for Common Materials

Perforated acoustic ceiling material 60%

Heavy curtains 50%

Carpeting 20%

Wood 5%

Plaster 3%

Clay tile 3%

Concrete 2%

The answer is C. Heavy curtains

two charges are fixed in place on the x-axis as shown. the charge at x = 0 is negative and has magnitude q = 2 μcoulombs (1 μcoulomb = 10-6 coulombs). the charge at x = d, (d = +12 cm), is positive and has magnitude q = 4 μcoulombs. find a point x = xo along the x-axis at which the electric field is zero.

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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