$$_{92}^{238}A \to _{90}^{234}B + _2^4D + Q$$

In the given nuclear reaction, the approximate amount of energy released will be:

[Given, mass of $${ }_{92}^{238} \mathrm{~A}=238.05079 \times 931.5 ~\mathrm{MeV} / \mathrm{c}^{2},$$

mass of $${ }_{90}^{234} B=234 \cdot 04363 \times 931 \cdot 5 ~\mathrm{MeV} / \mathrm{c}^{2},$$

mass of $$\left.{ }_{2}^{4} D=4 \cdot 00260 \times 931 \cdot 5 ~\mathrm{MeV} / \mathrm{c}^{2}\right]$$

A $$12.5 \mathrm{~eV}$$ electron beam is used to bombard gaseous hydrogen at room temperature. The number of spectral lines emitted will be:

The energy of $$\mathrm{He}^{+}$$ ion in its first excited state is, (The ground state energy for the Hydrogen atom is $$-13.6 ~\mathrm{eV})$$ :

Two radioactive elements A and B initially have same number of atoms. The half life of A is same as the average life of B. If $$\lambda_{A}$$ and $$\lambda_{B}$$ are decay constants of A and B respectively, then choose the correct relation from the given options.