The material used for a solar cell should have a band gap:

In an $LED$,when forward bias is increased (starting from zero),the intensity of emitted light will:

The active area of a solar cell is $......$ so that the power obtained $......$.

Explain the design,working,uses,and benefits of a light-emitting diode $(LED)$.

$A$ $p-n$ junction photodiode is fabricated from a semiconductor with a band gap of $2.5 eV$. It can detect a signal of wavelength: (Given: Planck's constant $h = 6.6 \times 10^{-34} Js$,speed of light $c = 3 \times 10^8 m/s$,elementary charge $e = 1.6 \times 10^{-19} C$)

Statement $-1$: $A$ photodiode operates in reverse bias.
Statement $-2$: The fractional change due to the photo-effects on the minority carrier dominated reverse bias current is more easily measurable than the fractional change in the forward bias current.