2. Questions Bank
  3. JEE Main & Advanced
  4. Physics
  5. Wave Mechanics

JEE Main & Advanced Physics Wave Mechanics Question Bank Self Evaluation Test - Waves

  • question_answer
    Two trains move towards each other with the same speed. The speed of sound is 340 m/s. If the height of the tone of the whistle of one of them heard on the other changes 9/8 times, then the speed of each train should be

    A)  20 m/s

    B)  2 m/s

    C) 200 m/s

    D) 2000 m/s

    Correct Answer: A

    Solution :

    [a] Here,   \[v'=\frac{9}{8}v\] Source and observer are moving in opposite direction, therefore, apparent frequency \[v'=v\times \frac{(v+u)}{(v-u)}\Rightarrow \frac{9}{8}\,v=v\times \frac{340+u}{340-u}\] \[\Rightarrow \,u=\frac{340}{17}=20\,m/\sec \]


You need to login to perform this action.
You will be redirected in 3 sec spinner