Q136 / 160 · AP EAMCET 2010 · Physics

Two coherent sources whose intensity ratio is $64: 1$ produce interference fringes. The ratio of intensities of maxima and minima is

  • A
    $9: 7$
  • B
    $8: 1$
  • Correct answer
    C
    $81: 49$
  • D
    $81: 7$

Solution

The ratio of intensities of maxima and minima $\frac{I_{\max }}{I_{\min }}=\frac{\left(\sqrt{I_1}+\sqrt{I_2}\right)^2}{\left(\sqrt{I_1}-\sqrt{I_2}\right)^2}$ $=\frac{(\sqrt{64}+\sqrt{1})^2}{(\sqrt{64}-\sqrt{1})^2}$ $\frac{I_{\max }}{I_{\min }}=\frac{(8+1)^2}{(8-1)^2}=\frac{81}{49}$

Hence, the correct answer is option: 'C'.

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