NEET Sample Paper NEET Sample Test Paper-15

  • question_answer If two waves of same frequency and same amplitude respectively, on superposition, produce a resultant disturbance of the same amplitude, the waves differ in phase by:

    A)  \[\pi \]                         

    B) \[\frac{2\pi }{3}\]

    C)  \[\frac{2\pi }{3}\]                              

    D)  \[3\pi \]

    Correct Answer: B

    Solution :

    Let\[{{A}_{R}}\]be the amplitude of resultant disturbance. \[{{A}_{R}}=\sqrt{A_{1}^{2}+A_{2}^{2}+2{{A}_{1}}{{A}_{2}}\cos \Phi }\] But, \[{{A}_{R}}=A\] \[\therefore \]\[A=\sqrt{2{{A}^{2}}(1+cos\Phi )}=\sqrt{4{{A}^{2}}{{\cos }^{2}}\frac{\Phi }{2}}=2A\cos \frac{\Phi }{2}\] or \[\Phi =\frac{2\pi }{3}.\] Hence, the correction option is [b].

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