In $Ulothrix$,$Spirogyra$,and $Chlamydomonas$,at what stage does meiosis occur?

$A$ rod $P$ of length $1 \ m$ is hinged at one end $A$ and there is a ring attached to the other end. Another long rod $Q$ is hinged at $B$ and it passes through the ring. The rod $P$ is rotated about an axis which is perpendicular to the plane in which both the rods are present and the variation between the angles $\theta$ and $\phi$ are plotted as shown. The distance between the hinges $A$ and $B$ is ....... $m$.

For the Bohr's first orbit of circumference $2\pi r$,the de-Broglie wavelength of the revolving electron will be

Lactose is composed of .......

On closing an open organ pipe from one end,it is noticed that the frequency of the third harmonic is $50 ~Hz$ more than the fundamental frequency of vibration in the open organ pipe. The fundamental frequency of the open organ pipe is (in $~Hz$)

Which of the following reagents reacts with benzaldehyde to produce $1$-phenylethanol?