The branch of botany that deals with the study of algae is known as:

The resistance of a wire is $R$. If the length of the wire is doubled by stretching,then the new resistance will be

The equation of the tangent at $(-4, -4)$ on the curve $x^2 = -4y$ is

If $x=a\left\{\cos \theta+\log \tan \left(\frac{\theta}{2}\right)\right\}$ and $y=a \sin \theta$,then $\frac{d y}{d x}$ is equal to

If the maximum velocity with which an electron can be emitted from a photocell is $4 \times 10^8 \,cm/sec$,the stopping potential is ............ $V$ (mass of electron $= 9 \times 10^{-31} \,kg$).