In a semiconductor,

What is the crystalline structure of an intrinsic semiconductor?

Statement-$1$: The temperature coefficient of resistance of an intrinsic semiconductor is negative.
Statement-$2$: As temperature increases,more charge carriers are released into the conduction band.

$A$ solid which is transparent to visible light and whose electrical conductivity increases with temperature is formed by:

The energy band gap of $Si$ is ........ $eV$.

What is the maximum wavelength of electromagnetic radiation that can create an electron-hole pair in a material with a band gap of $0.7 \ eV$? (Planck's constant $h = 4.136 \times 10^{-15} \ eV \cdot s$, velocity of light $c = 3 \times 10^8 \ m/s$).