Which part of the tobacco plant is infected by $Meloidogyne$ $incognita$?

The ratio of the magnetic field at the centre of a current-carrying circular wire and the magnetic field at the centre of a square coil made from the same length of wire will be

If $\operatorname{cosec} \theta = \frac{p+q}{p-q}$,then $\cot \left(\frac{\pi}{4} + \frac{\theta}{2}\right)$ is equal to

$A$ long wire carries a steady current. It is bent into a circle of one turn and the magnetic field at the centre of the coil is $B$. It is then bent into a circular loop of $n$ turns. The magnetic field at the centre of the coil will be

The refractive index of the material of a double convex lens is $1.5$ and its focal length is $5 ~cm$. If the radii of curvature are equal,the value of the radius of curvature (in $cm$) is

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