A $$p$$-$$n$$ junction $$(D)$$ shown in the figure can act as a rectifier. An alternating current source $$(V)$$ is connected in the circuit.

The current $$(I)$$ in the resistor $$(R)$$ can be shown by :

The logic circuit shown below has the input waveforms $$'A'$$ and $$'B'$$ as shown. Pick out the correct output waveform.

Output is

The transition from the state $$n=4$$ to $$n=3$$ in a hydrogen like atom result in ultra violet radiation. Infrared radiation will be obtained in the transition from :

The surface of a metal is illuminated with the light of $$400$$ $$nm.$$ The kinetic energy of the ejected photoelectrons was found to be $$1.68$$ $$eV.$$ The work function of the metal is : $$\left( {hc = 1240eV.nm} \right)$$