The colour of the positive column in a gas discharge tube depends on

Which of the following spectra contains all frequencies from the high to the low frequency range?

In the absorption spectrum of $Na$,the missing wavelength$(s)$ are:

The collision of an electron with kinetic energy $5.5 eV$ and a hydrogen atom in its ground state can be described as

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 $\mathring{A}$?

From which source are a continuous emission spectrum and a line absorption spectrum simultaneously obtained?