In hydrogen atom, the energy of electron in first and third orbit is ' $E_1$ ' and' $E_3$ ' respectively. If $E_3=x E_1$ then the value of $x$ will be

A radioactive element A decays into radioactive element C by the following processes in succession.

$\mathrm{A} \rightarrow \mathrm{B}+{ }_2 \mathrm{H}_{\mathrm{e}}^4 ; \mathrm{B} \rightarrow \mathrm{C}+2 \mathrm{e}^{-}$Then elements

${ }_{88} \mathrm{R}_{\mathrm{a}}^{226}$ is converted into ${ }_{82} \mathrm{P}_{\mathrm{b}}^{206}$ by emission of alpha ( $\alpha$ ) and beta ( $\beta$ ) particles. The number of alpha and beta particles emitted are respectively

Out of the following transitions in hydrogen atom, identify the transition which emits photons of highest frequency.