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Two sine waves of same frequency are impressed of the x and y plates of a CRO and the Lissajous figure seen is shown in the given figure. The phase difference between the signals is
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- 30° or 330° or 150° or 210°
- 30° or 330° or 150°
- 30° or 330°
- 30°
Correct Option: C
When major area of the Lissajous figure lies in the 1st and 3rd quadrant, then the angle is within 0 and ± 90°. If the loop lies in 2nd and 4th quadrant, then the angle is 180° – θ where θ is within 0 and + 90°.
In the present case the angle is given by
θ = sin–1 (Y1 /Y2) = sin–1 0.5 = 30°
Hence, the phase difference is 30° or – 30°,
i.e. 30° or 300°.
Y1 is the deflection on the Y-plates when X-plates deflection is zero, i.e. when Vx (t) = 0 and Vy (t) = Vmy sin φ and Y2 is the deflection due to Vmy.
