The longest wavelength line in the Lyman series of the $H$ atom spectrum is $:-$

Supposing the electron is present in the $4^{th}$ energy level of $H$ atom. When the electron returns to the ground state,the possible transitions would be:

Values of work function $(W_0)$ for a few metals are given below:

Metal	$Li$	$Na$	$K$	$Mg$	$Cu$	$Ag$
$W_0 / eV$	$2.42$	$2.3$	$2.25$	$3.7$	$4.8$	$4.3$

The number of metals which will show photoelectric effect when light of wavelength $400 \ nm$ falls on it is $........$.
Given: $h = 6.6 \times 10^{-34} \ J \ s$,$c = 3 \times 10^8 \ m \ s^{-1}$,$e = 1.6 \times 10^{-19} \ C$

The ground state energy of hydrogen atom is $-13.6 \ eV$. The energy of the second excited state of $He^{+}$ ion in $eV$ is:

If the radius of the first orbit of a hydrogen-like ion is $1.763 \times 10^{-2} \ nm$, the energy associated with that orbit (in $J$) is

For a hydrogen atom,which of the following electron transitions requires the highest energy?