Question

In an interference pattern produced by two identical slits, the intensity at the site of the central maximum is I. The intensity at the same spot when either of the two slits is closed is $I_{\circ }$. We must have:

• A. $I=I_{\circ }$
• B. $I=2I_{\circ }$
• C. $I=4I_{\circ }$
• D. $I$ and $I_{\circ }$ are not related

Answer 1

Answer: (C)

$I=4I_{\circ }$

In case of constructive interference of waves due to 2 slits is, the intensity of central maxima is given by,

$E^2=E_1^2+E_2^2+2E_1{E}_2$

where E is the amplitude. For coherent sources, $E^2=I$

Hence, $I=I_0+I_0+2I_o$

Or $I=4$ $I_0$