$A$ glass convex lens is of refractive index $1.55$ with both faces of same radius of curvature. What will be the radius of curvature if the focal length is to be $20 \text{ cm}$ (in $\text{ cm}$)?

The classical example of adaptive radiation in the development of new species is:

There is a rectangular sheet of dimension $(2m-1) \times (2n-1)$,where $m > 0, n > 0$. It has been divided into squares of unit area by drawing lines perpendicular to the sides. Find the number of rectangles having sides of odd unit length.

Phototropic curvature is the result of uneven distribution of

If $\alpha, \beta, \gamma$ are the roots of the equation $x^3-6x^2+11x-6=0$ and if $a=\alpha^2+\beta^2+\gamma^2$,$b=\alpha\beta+\beta\gamma+\gamma\alpha$ and $c=(\alpha+\beta)(\beta+\gamma)(\gamma+\alpha)$,then the correct inequality among the following is

What is the function of the radula?