In Franck-Hertz experiment, the first dip in the current-voltage graph for hydrogen is observed at $$10.2 \mathrm{~V}$$. The wavelength of light emitted by hydrogen atom when excited to the first excitation level is ________ nm. (Given hc $$=1245 \mathrm{~eV} \mathrm{~nm}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$$).

An atom absorbs a photon of wavelength $$500 \mathrm{~nm}$$ and emits another photon of wavelength $$600 \mathrm{~nm}$$. The net energy absorbed by the atom in this process is $$n \times 10^{-4} ~\mathrm{eV}$$. The value of n is __________. [Assume the atom to be stationary during the absorption and emission process] (Take $$\mathrm{h}=6.6 \times 10^{-34} ~\mathrm{Js}$$ and $$\mathrm{c}=3 \times 10^{8} \mathrm{~m} / \mathrm{s}$$ )

A monochromatic light is incident on a hydrogen sample in ground state. Hydrogen atoms absorb a fraction of light and subsequently emit radiation of six different wavelengths. The frequency of incident light is $$x \times 10^{15} \mathrm{~Hz}$$. The value of $$x$$ is ____________.

(Given h $$=4.25 \times 10^{-15} ~\mathrm{eVs}$$ )

The stopping potential for photoelectrons emitted from a surface illuminated by light of wavelength 6630 $$\mathop A\limits^o $$ is 0.42 V. If the threshold frequency is x $$\times$$ 10¹³ /s, where x is _________ (nearest integer).

(Given, speed light = 3 $$\times$$ 10⁸ m/s, Planck's constant = 6.63 $$\times$$ 10^$$-$$34 Js)