A) \[2\]
B) \[4\]
C) \[6\]
D) \[8\]
Correct Answer: B
Solution :
: Frequency of tuning fork (source), \[\upsilon =338Hz\] Velocity of sound, \[\upsilon =340\text{ }m{{s}^{-1}}\] When the person is moving towards the wall, the frequency of sound reaching the wall is \[\upsilon =\frac{\upsilon \upsilon }{\upsilon -{{\upsilon }_{s}}}\] ??.(i) On reflection wall acts as source and person is the listener moving towards the source. So the frequency heard by the person after reflection from the wall is \[\upsilon =\left[ \frac{\upsilon +{{\upsilon }_{L}}}{\upsilon -{{\upsilon }_{S}}} \right]\upsilon \] ??..(ii) Substituting the value of v from Eq. (i) in (ii), we get \[\upsilon =\left[ \frac{\upsilon +{{\upsilon }_{L}}}{\upsilon -{{\upsilon }_{S}}} \right]\upsilon =\left( \frac{\upsilon +{{\upsilon }_{S}}}{\upsilon -{{\upsilon }_{S}}} \right)\upsilon \] [As \[{{\upsilon }_{L}}={{\upsilon }_{S}}\]] \[=\left[ \frac{340+2}{340-2} \right]338=\frac{342}{338}\times 338=342Hz\] \[\therefore \]Number of beats heard per second \[=\upsilon -\upsilon \] \[=342-338=4\]
You need to login to perform this action.
You will be redirected in
3 sec
