Question

The intensity of central fringes in the interference pattern produced by two identical slits is $I$. When one of the slits is closed then the intensity at the same point is $I_o$. The relation between the $I$ and $I_o$ is

• A. $I=4I_o$
• B. $I=2I_o$
• C. $I=I_o$
• D. $I=\frac{I_o}{2}$

Answer 1

Answer: (A)

$I=4I_o$

when one of the slit is closed the intensity is only due to the remaining one hence the resultant intensity is same as the intensity of source $I_o$
when the two slits are oprn then the intensity is $I=(\sqrt{I_o}+\sqrt{I_o}{)}^2=4I_o$
option $A$ is correct