In a single slit diffraction pattern, identify the incorrect...

In a single slit diffraction pattern, the central maximum has an angular width of $\dfrac{2\lambda}{a}$, whereas the secondary maxima have an angular width of $\dfrac{\lambda}{a}$. Thus, the fringes have unequal widths.

The intensity of the central maximum is maximum, and the intensity of the successive secondary maxima decreases rapidly (approximately $\dfrac{I_0}{22}$, $\dfrac{I_0}{61}$, etc.). Thus, the fringes have unequal intensities.

Therefore, the statement that the fringes have equal width and equal intensity is incorrect.

Answer: The fringes have equal width and equal intensity.