If the energy gap of a semiconductor used for the fabrication of an $LED$ is nearly $1.9 \ eV$, then the color of the light emitted by the $LED$ is

In a $PN$ junction photocell,the value of the photo-electromotive force produced by monochromatic light is proportional to

The laptop PCs,modern electronic watches,and calculators use the following for display:

Consider a situation in which reverse biased current of a particular $P-N$ junction increases when it is exposed to light of wavelength $\lambda \le 621 \, nm$. During this process,enhancement in carrier concentration takes place due to the generation of hole-electron pairs. The value of the band gap is nearly (in $eV$):

The material suitable for making a solar cell is

The $I-V$ characteristics of a photodiode for different illumination intensities $I_1, I_2, I_3$ and $I_4$ are shown in the figure. Which of the following represents the maximum intensity?