Two planets $P_{1}$ and $P_{2}$ with equal mass have radii $R_{1}$ and $R_{2}$, respectively, where $R_{2}=\frac{R_{1}}{2}$. The escape speeds of $P_{1}$ and $P_{2}$ are $v_{1}$ and $v_{2},$ respectively. Then $\frac{v_{2}}{v_{1}}$ is:

Which of the following struture is not a part of the male reproductive system?

Consider the following nuclear reaction ${}^{238}U\longrightarrow{}^{234}Th+{}^{4}He$. Take masses of ${}^{238}U$, ${}^{234}Th$ and ${}^{4}He$ as 238.050 u, 234.043 u and 4.003 u, respectively. The Q value for the reaction, in keV, is: [Given: $1~u=931.5~MeV~c^{-2}$]

A ray of light with wavelength $\lambda$ is incident on three different photoelectric cells namely 1, 2 and 3. The threshold wavelength of these photoelectric cells are $\lambda_{1}$, $\lambda_{2},$ and $\lambda_{3,}$ respectively and the magnitude of stopping potentials of these cells are $V_{1}$, $V_{2}$ and $V_{3},$ respectively. The relation between $\lambda$ and threshold wavelengths are $\lambda_{1}\lambda$ and $\lambda_{3}>>\lambda$. The correct option is:

In an acidic medium, 10 mL of 0.25 M oxalic acid is titrated with $KMnO_{4}$ solution. If the volume of $KMnO_{4}$ solution required to reach end point is 10 mL, the strength of the $KMnO_{4}$ solution is