In the diffraction pattern of a single slit,the width of the secondary maxima compared to the central maximum is:

The condition for diffraction is

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.

For the visibility of a diffraction pattern of a wave of light,the size of the slit or obstacle should be

$A$ plane wavefront of monochromatic light is incident normally on a narrow slit. $A$ diffraction pattern is formed on a screen. What is the phase difference between the waves originating from the top and bottom edges of the slit at the position of the first minimum?

$A$ single slit diffraction experiment is performed to determine the slit width using the equation,$\frac{b d}{D} = m \lambda$,where $b$ is the slit width,$D$ is the distance between the slit and the screen,$d$ is the distance between the $m^{\text{th}}$ diffraction maximum and the central maximum,and $\lambda$ is the wavelength. $D$ and $d$ are measured with scales of least count of $1 \ cm$ and $1 \ mm$,respectively. The values of $\lambda$ and $m$ are known precisely to be $600 \ nm$ and $3$,respectively. The absolute error (in $\mu m$) in the value of $b$ estimated using the diffraction maximum that occurs for $m=3$ with $d=5 \ mm$ and $D=1 \ m$ is $.....$