The condition for diffraction is

In a single-slit diffraction experiment, the slit is illuminated by light of two wavelengths $\lambda_1$ and $\lambda_2$. It is observed that the $2^{nd}$ order diffraction minimum for $\lambda_1$ coincides with the $3^{rd}$ diffraction minimum for $\lambda_2$. Then:

Two wavelengths $590 \ nm$ and $596 \ nm$ of sodium light are used one after another to study the diffraction taking place at a single slit of aperture $2.4 \ mm$. The distance between the slit and the screen is $2 \ m$. The separation between the positions of the first secondary maximum of the diffraction pattern obtained in the two cases is:

$A$ 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 Fraunhofer diffraction due to a single slit,the direction of the second secondary maximum is given by ....... ($a$ is the width of the slit).

Red light is generally used to observe the diffraction pattern from a single slit. If blue light is used instead of red light,then the diffraction pattern: