Question

Diffraction pattern of a single slit consists of a central bright band which is

• A. Wide, and is flanked by alternate dark and bright bands of decreasing intensity
• B. Narrow, and is flanked by alternate dark and bright bands of equal intensity
• C. Wide, and is flanked by alternate dark and bright bands of equal intensity
• D. Narrow and is flanked by alternate-dark and bright bands of decreasing intensity

Answer 1

Answer: (A)

Wide, and is flanked by alternate dark and bright bands of decreasing intensity

We know that the width of the central diffraction maximum is inversely proportional to the width of the slit. If we increase the width size, $a$, the angle $\theta$ at which the intensity first becomes zero decreases, resulting in a narrower central band. And if we make the slit width smaller, the angle $\theta$ increases, giving a wider central band. Hence option A is well suited to it.