O₂ molecule consists of two oxygen atoms.In the molecule, nuclear force between the nuclei of the two atoms

1

(a)

is not important because nuclear forces are short-ranged

(b)

is as important as electrostatic force for binding the two atoms 

(c)

cancels the repulsive electrostatic force between the nuclei

(d)

is not important because oxygen nucleus have equal number of neutrons and protons.

The gravitational force between a H-atom and another particle' of mass m will be given by Newton's law \(F=G \frac{M m}{r^{2}}\), where r is in km

1

(a)

Gravitational mass of H-atom

(b)

Effective mass of H-atom

(c)

Nuclear mass of H-atom

(d)

Mass of electrons in H-atom

When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom

1

(a)

do not change for any type of radioactivity

(b)

change for a and β-radioactivity but not for γ-radioactivity 

(c)

change for a-radioactivity but not for others

(d)

change for β-radioactivity but not for others

In a nuclear reactor, moderators slow down the neutrons which come out in a fission process. The moderator used have light nuclei. Heavy nuclei will not serve the purpose, because

1

(a)

they will break up

(b)

elastic collision of neutrons with heavy nuclei will not slow them down

(c)

the net weight of the reactor would be unbearably high

(d)

substances with heavy nuclei do not occur in liquid or gaseous state at room temperature

In fusion reaction occurring in the sun,

1

(a)

hydrogen is converted into carbon

(b)

hydrogen and helium are converted into carbon and other heavier metals/elements

(c)

helium is converted into hydrogen

(d)

hydrogen is converted into helium