In a single slit diffraction pattern:

In Fraunhofer diffraction by a single slit,if the slit width is $a$,the wavelength is $\lambda$,and the focal length of the lens is $f$,what is the linear width of the central maximum?

How will the diffraction pattern change when yellow light is replaced by blue light? The fringes will be

Light of wavelength $6000 \ \mathring{A}$ is incident on a slit. The width of the slit is $0.30 \ mm$. A screen is placed at a distance of $2 \ m$ from the slit. Find the width of the central maximum in $mm$.

Assertion : When a tiny circular obstacle is placed in the path of light from some distance,a bright spot is seen at the centre of the shadow of the obstacle.
Reason : Destructive interference occurs at the centre of the shadow.

In the diffraction pattern, the first maximum is at $30^{\circ}$, when a monochromatic light of wavelength $\lambda$ is incident on a slit of width $a$. For the same wavelength, if the slit width is changed, so that the first maximum is at $45^{\circ}$, by how much is the slit width changed?