If the longest wavelength of the spectral line of the Paschen series of $Li^{2+}$ ion spectrum is $x \ \mathring{A}$,then the longest wavelength (in $\mathring{A}$) of the Lyman series of the hydrogen spectrum is

The limiting line in the Balmer series will have a frequency of (Rydberg constant,$R_{\infty} = 3.29 \times 10^{15} \ s^{-1}$)

What is the maximum number of different spectral lines obtained when a sample of a large number of $H$-atoms in the $5^{th}$ excited state makes transitions to the ground state,given that no lines are emitted in the Balmer series?

The value of the work function of a metal $X$ is $3.1 \ eV$. What is its threshold frequency (in $Hz$)? (Given: $h = 6.62 \times 10^{-34} \ J \cdot s$)

Lifetimes of the molecules in the excited states are often measured by using pulsed radiation source of duration nearly in the nanosecond range. If the radiation source has the duration of $2 \, ns$ and the number of photons emitted during the pulse source is $2.5 \times 10^{15}$,calculate the energy of the source.

Which of the following models states that "In an atom,the positive charge is uniformly distributed and electrons are embedded into it"?