The width of central maximum \(\frac{2D\lambda}{a}\)

If the width of the slit is made double of the original, the width of the central diffraction band will reduce to half. The intensity of the central diffraction band coil become four times.

Correct Answer – B
The angular width of the central maximum is `2lambda//a` where a is the width of the slit. If the value of a is doubled, the angular width of the central maximum decreases to half its earlier value. This implies that the central maximum becomes much sharper. Furthermore if a is doubled, the intensity of the central maximum becomes four times. Thus the central maximum becomes much sharper and brighter.

The angular width of central diffraction band `=(2lamda)/(q)alpha(1)/(a),` i.e., when slit width is doubled the width of central band becomes half of the initial value. As intensity of central maximum `alpha a^(2),` if slit width is doubled, the intensity becomes four times.