Question

Path difference between two waves from a coherent sources is 5 nm at a point P. Wavelength of these waves is 100 $\mathring{A}$. Resultant intensity at point P if intensity of sources is $l_0$ and $4l_0$

• A. Zero
• B. $l_0$
• C. $5l_0$
• D. $3l_0$

Answer 1

The correct option is B $l_0$

$\begin{array}{c}\Delta x=5\times {10}^{-9}m\\ \Delta \varphi =\frac{2\pi }{\lambda }\Delta x\\ =\frac{2\pi \times 5\times {10}^{-9}}{100\times {10}^{-10}}\\ =\pi \\ Now,\\ I=I_0+4I_0+2\sqrt{I_0}\sqrt{4I_0}\cos \varphi \\ =5I_0+4I_0\left[\cos \pi \right]\\ =I_0\\ \therefore resula\tan tintensity=I_0\\ Hence,optionBisthecorrectanswer.\end{array}$