Question

The intensity of principal maxima in the single slit diffraction pattern is $I_o$? What will be the intensity when slit width is doubled?

• A. $2I_o$
• B. $4I_o$
• C. $I_o$
• D. $\frac{I_0}{2}$

Answer 1

Answer: (C)

$I_o$

Intensity at screen is given by-
$I=I_0\times \frac{{\left(\sin \frac{\pi a\sin \theta }{\lambda }\right)}^2}{{\left(\frac{\pi a\sin \theta }{\lambda }\right)}^2}$
where, a is slit size,and $\theta$ is angle subtended by interfering light ray on screen.
for principal(central) maxima- $(\theta \to 0)$
$I_{central}=I_0$ ....(independent of slit size "a")