Line spectrum contains information about

The nature of the sun's spectrum is

Match the appropriate pairs from List-$I$ and List-$II$:

List-$I$	List-$II$
$1$. Nitrogen molecules	$(A)$ Continuous spectrum
$2$. Incandescent solids	$(B)$ Absorption spectrum
$3$. Fraunhofer lines	$(C)$ Band spectrum
$4$. Electric arc between iron rods	$(D)$ Emission spectrum

Pick out the correct statement from the following:

An electron passing through a potential difference of $4.9 \ V$ collides with a mercury atom and transfers it to the first excited state. What is the wavelength of a photon corresponding to the transition of the mercury atom to its normal state in $\mathring{A}$?

When the potential of the second excited state of an atom is $108.8 \ V$,the recoil energy of the atom is ...... Joules.