If a classroom door is open just a small amount, we can hear sounds coming from the room but we can't see what is going on inside the room because

To observe diffraction,the size of the obstacle

In a single slit diffraction experiment, the width of the slit is reduced. What happens to the linear width of the principal maxima?

Determine the angular separation between the central maximum and the first-order maxima of the diffraction pattern due to a single slit of width $0.25\, mm$ when light of wavelength $5890\,\mathring{A}$ is incident on it.

$A$ diffraction pattern is obtained by using a beam of red light. What will happen if the red light is replaced by blue light?

Which of the following are true for a single slit diffraction?
$(A)$ Width of central maxima increases with increase in wavelength keeping slit width constant.
$(B)$ Width of central maxima increases with decrease in wavelength keeping slit width constant.
$(C)$ Width of central maxima increases with decrease in slit width at constant wavelength.
$(D)$ Width of central maxima increases with increase in slit width at constant wavelength.
$(E)$ Brightness of central maxima increases for decrease in wavelength at constant slit width.