| A sound source emitting sound with frequency \[{{f}_{0}}\] is moving towards a fixed wall. Now, consider three observers \[{{O}_{1}},{{O}_{2}}\]and \[{{O}_{3}}\] as shown below. |
 |
| Ratio of frequencies observed by observers \[{{f}_{1}} :{{f}_{2}}:{{f}_{3}}\] is (take, \[{{\upsilon }_{s}}=\] speed of source, \[\upsilon =\] speed of sound in air and assume that \[{{O}_{3}}\] receives only reflected sound and \[{{v}_{s}}=\frac{v}{2}\]) |
A) \[1:2:3\]
B) \[6:3:2\]
C) \[3:2:1\]
D) \[2:6:9\]
Correct Answer: D
Solution :
| For \[{{O}_{1}}\], observed frequency |
| \[{{f}_{1}}={{f}_{0}}\left( \frac{\upsilon }{\upsilon +{{\upsilon }_{s}}} \right)\] |
| Also, \[{{f}_{2}}={{f}_{0}}\left( \frac{\upsilon }{\upsilon -{{\upsilon }_{s}}} \right)\] |
| And \[{{f}_{3}}=\left( \frac{\upsilon +{{\upsilon }_{s}}}{\upsilon -{{\upsilon }_{s}}} \right){{f}_{0}}\] |
| So, \[{{f}_{1}}:{{f}_{2}}:{{f}_{3}}::2:6:9\] |
You need to login to perform this action.
You will be redirected in
3 sec
