For Bragg's diffraction by a crystal to occur,the $X$-ray of wavelength $\lambda$ and interatomic distance $d$ must satisfy which condition?

$A$ microwave of wavelength $2.0 \ cm$ falls normally on a slit of width $4.0 \ cm$. The angular spread of the central maxima of the diffraction pattern obtained on a screen $1.5 \ m$ away from the slit,will be: (in $^{\circ}$)

Light is incident normally on a diffraction grating through which the first order diffraction is seen at $32^\circ$. The second order diffraction will be seen at

$A$ plane wavefront $(\lambda = 6 \times 10^{-7} \, m)$ falls on a slit $0.4 \, mm$ wide. $A$ convex lens of focal length $0.8 \, m$ placed behind the slit focuses the light on a screen. What is the linear diameter of the second maximum in $mm$?

Light of wavelength $6000 \, \mathring{A}$ is incident on a slit of width $0.30 \, mm$. The screen is placed $2 \, m$ from the slit. Find the position of the first minima.

In a single slit diffraction pattern, the wavelength of light used is $628 \text{ nm}$ and slit width is $0.2 \text{ mm}$. The angular width of the central maximum is $\alpha \times 10^{-2} \text{ degrees}$. The value of $\alpha$ is . . . . . . . (Take $\pi = 3.14$)