$A$ monochromatic light of wavelength $6000 \text{ Å}$ is incident on a single slit of width $0.01 \text{ mm}$. If the diffraction pattern is formed at the focus of a convex lens of focal length $20 \text{ cm}$, the linear width of the central maximum is: (in $\text{ mm}$)

When a compact disc is illuminated by a source of white light,coloured 'lanes' are observed. This is due to

In a single slit diffraction pattern,identify the incorrect statement from the following.

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).

$A$ parallel beam of light of wavelength $\lambda$ is incident normally on a narrow slit. $A$ diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the second minimum of the diffraction pattern,the phase difference between the rays coming from the two edges of the slit is:

To observe diffraction,the size of the obstacle