Which is the wrong statement in the following sentences? $A$ device in which $P$ and $N$-type semiconductors are used is more useful than a vacuum tube because:

Assuming the ideal diode,draw the output waveform for the circuit given in the figure. Explain the waveform.

The energy of a photon in a monochromatic light of wavelength $621 \ nm$ matches with the band gap of a semiconducting material. Then the minimum energy required to create an electron-hole pair from the semiconductor is
[Take $hc = 1242 \ eV-nm$,where $h$ is Planck's constant and $c$ is speed of light in vacuum] (in $eV$)

Show the direction of the electric field that arises in a $p-n$ junction.

In forward bias,the width of the potential barrier in a $P-N$ junction diode:

The circuit shown in the figure contains two diodes,each with a forward resistance of $30 \, \Omega$ and infinite backward resistance. If the battery is $3 \, V$,the current through the $50 \, \Omega$ resistance (in ampere) is