$1$ mole of photons, each of frequency $2500 \ s^{-1}$, would have approximately a total energy of:

The frequency of the limiting line of the Lyman series in the hydrogen spectrum is ....

$A$ 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 $.....$

The energy of the second Bohr orbit of the hydrogen atom is $-3.4 \ eV$. The energy of the fourth Bohr orbit of the $He^{+}$ ion will be: (in $eV$)

$A$ metal surface is exposed to $500 \ nm$ radiation. The threshold frequency of the metal for photoelectric current is $4.3 \times 10^{14} \ Hz$. The velocity of the ejected electron is $....... \times 10^{5} \ ms^{-1}$ (Nearest integer).
[Use : $h=6.63 \times 10^{-34} \ Js, m_{e}=9.0 \times 10^{-31} \ kg$]

The ratio between kinetic energy and the total energy of the electrons of a hydrogen atom according to Bohr's model is