Question

When a single slit is replaced bydouble slit arrangement, the intensity of central maxima is increased by?

Answer 1

We know that the intensity due to single silt

$I_1=I_o(\frac{\sin\phi}{\phi})^2$

Intensity due to double slit

$I_2=I_o \cos^2(\frac{\phi}{2})$

From first and second,

$\frac{I_1}{I_2}=\frac{4\sin^2(\phi/2)}{\phi}$