Two speakers that are 12.0 m apart produce in-phase sound waves of frequency 245 hz in a room where the speed of sound is 340 m/s. a woman starts out at the midpoint between the two speakers. the room's walls and ceiling are covered with absorbers to eliminate reflections, and she listens with only one ear for best precision.

(a) why is this constructive interference?

(b) she now walks slowly toward one of the speakers. how far from the center must she walk before she first hears the sound reach a minimum intensity?

(c) how far from the center must she walk before she first hears the sound maximally enhanced?

a. constructive interference takes place.

b.  x = 0.34 m= 34 cm

c..  

Explanation:

Given

Distance between speakers = 12.0 m

frequency = 245 Hz,

speed of sound = 340 m/s,

a. For constructive interference we have

the path difference is

where m =  +/-1,+/-2,+/-3,..........

Wavelength of sound =

As women is at center or middle point, therefore the path difference at that point must be zero

Now the path difference   is an integral multiple of the wavlenght therefore constructive interference takes place.

b.

   for the  sound to reach a minimum intensity

Now if she moves x distance from current point then

for hearing minimum intensity the interference must be destructive therefore,

for m = 0

by putting the value of lamda = 1.38 and difference in distance as 2x

we get

 x = 0.34 m= 34 cm

c.

for the  sound to reach a maximum intensity

  for that m=1

freezing

deposition

condensation

explanation;

melting also called fusion is the process where solid becomes liquid, sublimation is the process where solid becomes gaseous without first changing to liquid, deposition involves change from gaseous to solid state, freezing involves change from liquid to solid, boiling or evaporation involves change of liquid to gaseous state, while condensation is the change from gaseous state to liquid state.

endothermic reactions involves absorption of heat from the surroundings or the environment while exothermic reactions involves loss of heat energy to the surroundings.

in this case, sublimation, evaporation and melting are endothermic reactions (gain energy from the environment) while, freezing, deposition and condensation are exothermic (loss of energy to the surroundings) reactions.