The wavelength of an electron and a neutron will become equal when the velocity of the electron is $$x$$ times the velocity of neutron. The value of $$x$$ is ____________. (Nearest Integer)

(Mass of electron is $$9.1 \times 10^{-31} \mathrm{~kg}$$ and mass of neutron is $$1.6 \times 10^{-27} \mathrm{~kg}$$ )

When the excited electron of a H atom from n = 5 drops to the ground state, the maximum number of emission lines observed are _____________.

If the work function of a metal is 6.63 $$\times$$ 10^{$$-$$19}J, the maximum wavelength of the photon required to remove a photoelectron from the metal is ____________ nm. (Nearest integer)

[Given : h = 6.63 $$\times$$ 10^{$$-$$34} J s, and c = 3 $$\times$$ 10^{8} m s^{$$-$$1}]

Consider the following set of quantum numbers.

n | 1 | m$$_1$$ | |
---|---|---|---|

A. | 3 | 3 | $$ - $$3 |

B. | 3 | 2 | $$ - $$2 |

C. | 2 | 1 | +1 |

D. | 2 | 2 | +2 |

The number of correct sets of quantum numbers is __________.