The first terrestrial plants are .......

The metal ion present in vitamin $B_{12}$ is

An electron of mass $m$ when accelerated through a potential difference $V$ has de-Broglie wavelength $\lambda$. The de-Broglie wavelength associated with a proton of mass $M$ accelerated through the same potential difference will be:

Let $A = \{ (x, y) : y = e^x, x \in R \} $ and $B = \{ (x, y) : y = e^{-x}, x \in R \} $. Then

In an $ac$ circuit $I = 100 \sin(200 \pi t)$. The time required for the current to achieve its peak value will be

The principal section of a glass prism is an isosceles triangle $ABC$ with $AB=AC$. The face $AC$ is silvered. $A$ ray of light is incident normally on the face $AB$ and after two reflections,it emerges from the base $BC$ perpendicular to the base. Angle $BAC$ of the prism is (in $^{\circ}$)