The solar spectrum is an example of

An energy of $24.6\ eV$ is required to remove one of the electrons from a neutral helium atom. The energy (in $eV$) required to remove both the electrons from a neutral helium atom is

$A$ photon collides with a stationary hydrogen atom in the ground state inelastically. The energy of the colliding photon is $10.2 \ eV$. After a time interval of the order of a microsecond,another photon collides with the same hydrogen atom inelastically with an energy of $15 \ eV$. What will be observed by the detector?

Which of the following atoms has the lowest ionization potential?

When light emitted by a white hot solid is passed through a sodium flame,the spectrum of the emergent light will show

The number of completely filled shells for the element ${ }_{16} S ^{32}$ is