The resultant amplitude, when two waves of same frequency but with amplitudes a1 and a2 superimpose with a phase difference of π/2 will be
A
a21+a22
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B
√a21+a22
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C
a1−a2
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D
a1+a2
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Solution
The correct option is A√a21+a22 The equation of the two superimposing waves can be give by y1=a1sin(ωt) and y2=a2sin(ωt+π/2)=a2cos(ωt). So, the equation of the resultant wave is y=y1+y2=a1sin(ωt)+a2cos(ωt). Assuming a1=acos(ϕ) and a2=asin(ϕ), we get y=asin(ωt+ϕ). Here a21+a22=a2(sin2(ϕ)+cos2(ϕ))=a2⇒a=√a21+a22.