S1 and S2 are two sources of light which produce individually disturbance at point P given by →E1=3sinωt and →E2=4cosωt. Assuming −→E1 and −→E2 to be along the same line, the resultant of their super position is
A
5sin(ωt+53∘)
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B
5sin(ωt+37∘)
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C
5sin(ωt+45∘)
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D
5sin(ωt+30∘)
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Solution
The correct option is A5sin(ωt+53∘) A vector diagram for amplitude of waves at point P is shown in the figure.
Given, →E1=3sinωt
And, →E2=4sin(ωt+π2)
So, phase difference, ϕ=π2
Therefore, resultant amplitude
E=√E21+E22+2E1E2cosϕ
=√32+42+(2×3×4×cosπ2)=5
Also, the phase difference of the resultant disturbance is given by
tanθ=E2sinϕE1+E2cosϕ
=4sinπ23+4cosπ2=43
⇒θ=tan−1(43)=53∘
Hence, net disturbance, E=5sin(ωt+53∘)
Hence, option (A) is correct.
Why this question?
This question give you ides that amplitudes of waves can be added vectorially if the waves are on the same line.