Assertion Radioactive nuclei emits $$\beta^{-}$$-particles.

Reason Electrons exist inside the nucleus.

A nuclear explosive is designed to deliver $$1 \mathrm{~MW}$$ power in the form of heat energy. If the explosion is designed with nuclear fuel consisting of $$U^{235}$$ to run a reactor at this power level for one year, then the amount of fuel needed is (Given energy per fission is $$200 \mathrm{~MeV}$$)

Assertion : A beam of charged particles is employed in the treatment of cancer.

Reason : Charged particles on passing through a material medium lose their energy by causing ionization of the atoms along their path.

Assertion : In He-Ne laser, population inversion takes place between energy levels of neon atoms.

Reason : Helium atoms have a metastable energy level.