The penetration of light into the region of geometrical shadow is called:

$A$ light ray of wavelength $\lambda$ is passing through a pinhole of diameter $D$ and the effect is observed on a screen placed at a distance $L$ from the pinhole. The approximations of geometrical optics are applicable, if

The phenomenon of diffraction occurs in .......

$A$ parallel beam of monochromatic light is incident on a narrow rectangular slit of width $1\,mm$. When the diffraction pattern is seen on a screen placed at a distance of $2\,m$, the width of the principal maxima is found to be $2.5\,mm$. The wavelength of light is $.............\mathring{A}$.

In a diffraction experiment from a single slit,the angular width of the central maximum does $NOT$ depend upon:

Two wavelengths of sodium light $590 \,nm$ and $596 \,nm$ are used one after another to study diffraction due to a single slit of aperture $2 \times 10^{-6} \,m$. The distance between the slit and the screen is $1.5 \,m$. The separation between the positions of the first maximum of the diffraction pattern obtained in the two cases is: (in $\,mm$)