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Two waves represented by \( y_{1}= \) \( 10 \sin (2000 \pi t) \) and \( y_{2}= \) \( 10 \sin (2000 \pi t+\pi / 2) \) are superimposed at any point at a particular instant. The resultant amplitude is?
- 10 units
- 20 units
- 14.1 units
- zero
Correct answer: 14.1 units
Solution
The two waves have the same amplitude, 10, and a phase difference of \(\pi/2\). For equal amplitudes \(A\) with phase difference \(\phi\), the resultant amplitude is \(2A\cos(\phi/2)\). Substituting gives \(2\cdot10\cdot\cos(\pi/4)=20\cdot\frac{\sqrt2}{2}=14.1\).
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