If the ratio of the nuclear radii of two atoms is $2: 3$ then the ratio of their mass numbers is:

The atomic mass of an element $10 X^{20}$ is 19.98170 amu. The binding energy per nucleon of that element is: [given mass of neutron = 1.00867amu and mass of proton = 1.00783 amu and 1amu = 931 MeV ]

An atom has a single electron. Its ground state energy is -30 eV and its first excited state energy is -8 eV . The atom is bombarded with a stream of photons, each of energy 15 eV .

Assuming the atom being in the ground state, which of the following statements is correct?

A. Atom gets excited to the first excited state and later emit photons of 22 eV

B. Atom absorbs energy continuously until 22 eV is accumulated and then gets excited

C. Atom will not get excited, and the transmitted light will have the same frequency as the incident light

D. Atom will absorb the photon and re-emit a photon of lower energy

A nucleus of uranium -235 absorbs a slow neutron and undergoes nuclear fission according to the reaction: ${ }_{92}^{235} U+{ }_0^1 n \rightarrow{ }_{56}^{141} B a+{ }_{36}^{92} K r+3{ }_0^1 n+Q$

If the average energy released per fission is 202 MeV , the energy released when 2.35 g of $U^{235}$ undergoes complete fission is approximately;

[Given $1 \mathrm{eV}=1.6 \times 10^{-19} \mathrm{~J}$, Avogadro number $=6.02 \times 10^{23}$ ]