Binding energy of a hydrogen atom is $13.6 \ eV$. The binding energy of a singly ionized helium atom is : ............ $eV$

$A$ $25 \ W$ bulb emits monochromatic yellow light of wavelength $0.57 \ \mu m$. Calculate the rate of emission of quanta per second.

What is the relation between radius, order of orbit, and nuclear charge for hydrogen-like species?

$A$ bulb emits monochromatic yellow light of the wavelength $0.57 \ \mu m$. If the rate of emission of quanta per second of the bulb is $14.33 \times 10^{19}$, the power of the bulb (in $Watt$) is $.....$

If change in energy $(\Delta E) = 3 \times 10^{-8} \ J$,$h = 6.64 \times 10^{-34} \ J \cdot s$ and $c = 3 \times 10^8 \ m/s$,then the wavelength of the light is:

When an electron in a hydrogen spectrum transitions from the $7^{th}$ energy level to the $1^{st}$ energy level,what is the total number of spectral lines produced?