An electron in the hydrogen atom jumps from $n^{th}$ energy state to the ground state. The wavelength so emitted illuminates a photosensitive material having work function $2.65$ eV. If the maximum kinetic energy of the emitted photoelectrons is $10.1$ eV, then the value of '$n$' is

The angular momentum of an electron in Bohr's hydrogen atom having energy $(-0.544)$ eV is
($h$ = Planck's constant)

The output Y of the following digital logic circuit will be '1' (one) for the inputs

In a common emitter transistor amplifier, AC current gain is $65$, the load resistance is $5400\,\Omega$ and input resistance of the transistor is $450\,\Omega$. The voltage gain is