The mass defect of $ { }_{2}^{4} He $ is $ 0.03 \ u $. The binding energy per nucleon of helium (in $ MeV $ ) is

If $m$ is the mass of the $_Z{X^A}$ nucleus,and $m_n$ and $m_p$ are the masses of a neutron and a proton respectively,then which of the following is correct?

$A$ nucleus of mass $ 20 u $ emits a $ \gamma $ photon of energy $ 6 MeV $. If the emission is assumed to occur when the nucleus is free and at rest, then the nucleus will have a kinetic energy nearest to (take $ 1 u = 1.6 \times 10^{-27} kg $): (in $keV$)

If the speed of light were $2/3$ of its present value,the energy released in a given atomic explosion will be decreased by a fraction:

When the atomic number $A$ of the nucleus increases,

The ratio of the orders of the spacings of nuclear energy levels and atomic energy levels is