Physics - Wave Optics Question with Solution | TestHub

The width of the diffraction bands is directly proportional to the wavelength of the light used, given by $\beta =\frac{\lambda D}{a}$.

The wavelength of blue light is less than the wavelength of red light (${\lambda }_{blue}<{\lambda }_{red}$).

Therefore, when red light is replaced by blue light, the width of the diffraction bands decreases.

This causes the diffraction bands to become narrower and crowded together.

Answer: diffraction bands become narrow and crowded together.