The device that can detect optical signals is

In a $p-n$ junction solar cell,the value of photo-electromotive force produced by monochromatic light is proportional to the

The semiconductor used for the fabrication of visible LEDs must at least have a band gap of (in $eV$)

$A$ family uses $8 \; kW$ of power.
$(a)$ Direct solar energy is incident on the horizontal surface at an average rate of $200 \; W$ per square meter. If $20 \%$ of this energy can be converted to useful electrical energy, how large an area is needed to supply $8 \; kW$?
$(b)$ Compare this area to that of the roof of a typical house.

$A$ photodiode is a device

What kind of diode is used as a photo detector?